PART IV

.

TOOLS AND APPLIANCES.

WORKSHOP FITTINGS.

=229.= Before proceeding to describe the various forms of lathes and the several small tools that the watchmaker should make for himself as occasion offers, either during his apprenticeship or immediately after, with a view to increase his manual skill or to extend his experience, it will be well that he take note of the principal conditions that should be satisfied by the ordinary tools that he will have to buy, as well as the precautions to be observed in their use and some improvements of which they are capable.

=230.= =The bench or board.= This should be fixed in front of a large window that affords a good light. The various hooks, recesses, etc., for holding files, hammers, etc., as well as the drawers, should be well in sight, not only in order that the hand can at once take hold of whatever tool is required, but also to enable the workman to restore them to their place immediately after use. By doing so he will have no occasion to retain on the bench any but those tools that are very frequently or continuously used.

It is an excellent habit, conducive both to well-planned and rapid work, and which can be easily acquired by a little attention during an apprenticeship, to always place the same tools in the same places, as the bench will then never be encumbered. By this means loss of time in turning over a number of objects in order to find one that may be small is frequently avoided.

This observation is of minor importance to specialists who require but a small number of tools; but it is of the first importance to a workman that is engaged in the repair of watches.

=231.= =The stool.= Those with cane seats are to be preferred. The height of the bench and stool should be so related that the muscles of the chest are not too much cramped, especially if the workman is engaged on an operation that occupies a long time and obliges him to maintain a stooping position. The stool with a screw is advantageous in this respect.

=232.= =The lamp.= Certain precautions in regard to artificial light have already been indicated in article =218=.

=233.= =Oilstones.= It is impossible to maintain the points of gravers in good condition if care is not taken to keep clean and flat the surface of the stone on which they are set; if it has suffered irregular wear, the level may be restored by rubbing the stone on a flat, smooth board, covered with a thin paste of fine sand and water. Most kinds of oil thicken on the surface rapidly, when the graver will slide over without being ground down at all, turning around in the hand and thus destroying the flat face and wearing the softer parts of the stone, rendering it uneven. A strong solution of potash or soda is very effective for removing this gummy mass; benzine is also recommended for the same purpose. Various substitutes for common oil are used; such as the mineral lubricating oils or petroleum. Dr. Latteux advocates the use of a mixture of alcohol and glycerine, the proportion of the latter decreasing as the extent of metallic surface in contact with the stone at once increases. Thus, for example, in setting a razor the stone will bite better if alcohol be in excess; but for a graver, of which only a small surface touches the stone, the amount of glycerine present should be relatively much greater.

=234.= =Circular oilstones.= Circular oilstones will be found very convenient for sharpening drills, gravers and other cutting tools, where it is desirable to have exact angles. An Arkansas or Turkey stone dressed down to circular form, and say 1½ inches in diameter, when mounted for the lathe will be found very useful. Apply the lubricant to the stone the same as you would to a flat one, and hold your graver or drill at the exact angle you wish the cutting edges to be and turn at a moderate speed. Truer angles and better work can be produced in this manner than by any other. Emery or corundum wheels can be mounted in a similar manner. Small circular stones can be obtained from material dealers and dental supply houses, in sizes varying from ½ × ⅛ to 3½ × ¾ inches. They can be mounted similar to Fig. 49, by turning down a piece of No. 30 Stubb’s steel wire to the size of the opening in your wheel and riveting the wheel firmly upon it. The best sizes for watchmakers’ use are ½ inch, 1 inch and 1½ inch in diameter.

[Illustration: _Fig. 49._]

=235.= =Small grindstones.= When it is necessary to remove a good deal from the face of a graver, the operation will take too long on the oilstone, and there would be considerable difficulty in maintaining the flat face; recourse must then be had to the grindstone, but it should be remembered that care is needful when using it. The grindstone must always be thoroughly wet in order to avoid heating the graver, as its cutting power would then be destroyed. The emery wheels described in paragraph =165= can be used for this purpose, but they are, for the most part, inconvenient on account of the rapid increase they occasion in the temperature of the metal. Some forms of emery wheel can, however, be moistened just as the grindstone.

When the cylindrical surface is rendered irregular by use, take a piece of sheet-iron, the tail of an old file or a cold chisel, and hold it with one hand firmly on a support against the edge of the stone, which is rotated by the other hand. The surface can thus be made smooth and true, providing it is only attacked gradually and the handle is not turned too rapidly. An excessive velocity will heat the iron, which is then less effective and is more rapidly worn down; whereas, with a slow motion, the iron will relatively wear little and the stone more. A rough diamond mounted at the extremity of a steel rod, affords an excellent means of trimming a grindstone, and is at the present day generally used in factories.

=236.= =Glasses.= Some particulars have already been given in regard to these simple microscopes in article =218=.

=237.= =Files.= A new file should never be used for steel; it is best to employ it for some time at first on brass, taking care not to use it too roughly. If employed to steel at once, or if sharp, quick strokes are applied, the cutting edges of the file will chip off, and the hard

## particles will be embedded in the metal operated upon; the work will

thus be bad, and the file itself deteriorated. A file that has been carefully used, and has passed gradually from brass to steel, will last four or five times as long, and will always work well.

Watchmakers often fit files into handles by driving them firmly into round holes in the handles; this practice frequently leads to the handles being cracked, and the following method is preferable: Take an old worn out file or a piece of iron of the same form as the tail of the file to be fitted; heat it several times to bright redness and drive it, when so heated, into the handle, taking care to maintain it perpendicular. A hole will thus be made of the required form, in which the file will hold without there being any occasion to apply excessive force in fixing it in position.

When the surface of a file is choked with particles of iron, copper, wood, etc., while the cutting edges are yet good, it can be cleaned as follows: Place the file for a few seconds in a hot lye of potash in water, and on withdrawal, dry it before the fire and brush the surface with a stiff brush.

=238.= To renew the cutting edges of files, either of the following methods can be adopted: 1. First clean the file with potash or soda dissolved in water, if greasy or resinous substances have to be removed; with hydrochloric acid if it is rusty; and by rubbing with a metallic brush or piece of coke if particles of iron, brass, lead, copper or tin have to be removed. The file is now immersed in a mixture of 1 part nitric acid, 3 parts sulphuric acid, and 7 parts water. As the action of the acids become less energetic owing to the combination with iron, the temperature of the mixture must be raised, since rapidity is a condition of success. The time during which the file should remain in this bath varies from 10 seconds to 100 or more, the roughening of fine-cut files being far more rapid than when they are of a coarser cut. On removal from the bath, immerse in lime wash, dry, and then cover them with a mixture of oil and turpentine by means of a brush, after which they are ready for use. 2. After being cleaned, as explained above, the file is supported in a dish full of water, resting on two cross wires, so that all its surface is in contact with the liquid. Now add strong nitric acid in the proportion of 1 part to 8 of the water, mix it thoroughly and allow it to remain for 25 minutes. Remove the file, and, after washing in water and rubbing with a hard brush, place it again in the bath, to which a second eighth part of acid is now added, and leave it for 50 minutes. Again remove and brush the file, add a sixteenth part of concentrated sulphuric acid, and replace the file in the bath. Then wash successively in pure water and in lime wash (to remove the last traces of acid), and dry. The file will be found to possess both the qualities and the appearance of a new one.

=239.= _To cut an equaling file._ It often happens that a workman is called upon to modify the shape of, for example, the bottom of a rectangular notch, and he is not provided with a file of suitable shape. In such a case he can adopt one of the following methods of extemporizing a file:

[Illustration: _Fig. 50._]

1. Clamping the small steel strip, L, Fig. 50, in a vice, cut the notches with a chisel, _n_, as follows: Holding _n_ a little inclined, cut the first notch, _i_. This will slightly raise the metal, presenting a rounded face at the back. To make the next cut, hold the chisel with its edge on L and, after drawing it backward until arrested by the back of _i_, incline it to the requisite amount and give a second blow with the hammer, then continue the operation till the whole is finished. A few trials will enable any workman to make a small file with sufficient accuracy for his purpose.

2. Employ an arrangement similar to that of the micrometer divider (=44=) only more rigid. A study of this article and examination of the corresponding figure will afford all the information that is necessary.

3. This is identical with the method of dividing a rule described in =46=, except that the divisions are closer together and the tracer is replaced by a revolving cutter with its axis a little inclined, to give the requisite slope to the teeth of the file. This cutter is supported in a hinged frame and provided with a washer of ivory or other such substance, as seen at _s_, Fig. 50, to determine the depth of cut.

=240.= _Beaupuy files and burnishers._ Most watchmakers are acquainted with the files and burnishers that M. Beaupuy has introduced for rapidly forming conical pivots, the main characteristic of which is that the corner presented to the pivot is rounded to the desired form and roughed; they do their work rapidly and well, but some skill is necessary in their management. To the instructions which accompany them we would add the following:

They must never be used when quite new on a pivot that is to be employed in a watch; it will be reduced too rapidly. The freshness must be worn off the cutting edges of the teeth by preliminary use.

The pressure must only be applied perpendicularly to the surface of the staff as in making a square-shouldered pivot; the file is held against the flat surface without pressure. A lateral force will have the effect of straining the pivot and causing it to break.

=241.= =Pliers, tweezers, etc.= It is advisable to have a considerable number of these, as their strength should always be proportional to the force that has to be applied to them. For example, if a pair of sliding tongs is used when a hand-vise is needed, the former will be strained beyond its limit of elasticity and the tool becomes nearly useless.

The same might occur with any other form of pliers or tweezers. In the hands of a good workman they will last for a long time, but if used unintelligently, without proportioning the size of tool to the force that has to be applied, taking up the first that comes to hand, all the tools will soon become unsatisfactory and the work itself will suffer. It is very desirable to have one or more pairs of brass pliers and tweezers for handling metal work without the risk of scratching.

=242.= =Compasses, gauges, micrometers, etc.= The common compass for measuring thickness, the douzieme gauge, is not always strictly accurate in its indications. The douzieme proper, has a scale divided into twelfths, though some patterns are now made that have a scale divided into tenths and hundreds of an inch and again there are others that measure the fractions of a millimeter. The greater majority of these tools on the American market are correctly divided, but we sometimes come across those of foreign make that are divided incorrectly and care should be used in selecting. In the inaccurate tools the objection is that the opening of the jaws gives a measure of a _chord_ whereas the displacement of the index measures the _arc_ of a circle. It follows from this, that, if the index is first arrested when pointing to 15, for example, and again when at 30, the interval between the jaws in the second case will not be exactly double the first. Before purchasing, it is well to test the gauge for accuracy in this regard by some reliable standard.

=243.= _Caliper for mainspring height, depth of sink, etc._ A simple instrument for taking such measurements is shown at G, Fig. 51.

[Illustration: _Fig. 51._]

The finger _a_ travels over a graduated arc whenever the rod _c_ is pressed inwards; _b_ is a fixed stop, with its extremity in the plane of _n_. Any movement of _a_ below _o_ measures the space traversed by _c_ within the line _b n_.

Laying a coiled mainspring, for example, on a plane surface, stand the base _n_ of the caliper upon it, and the end _c_ pressing on the table will be forced upwards and move the needle. To take the depth of a barrel, press _c_ on the bottom, allowing _b_ to rest on the edge of the cover recess.

It will be evident, from the figure, that _a_ and _c_ are connected by a spring passing around drums at corresponding axes. The smaller _j_ is, the more sensitive will the instrument become.

=244.= =Figure 8 caliper.= For ordinary work, the calipers to be bought at material stores will suffice; but when it is required to verify escape wheels, balances, etc., there is some risk of accidents in consequence of the variableness of the friction at the joint. To remove this source of danger, true the rubbing surfaces in the mandril and replace the brass discs at the center by similar discs of steel, then carefully re-make the rivet that forms a hinge, after oiling all the acting surfaces. The arms will now move with a uniform degree of stiffness, so that there need be no danger of jerks.

=245.= =Riveting stake and punch.= The holes in a riveting stake are made to increase downwards, so as to avoid any accident occurring through the oscillation of the axis. The riveting punches made of a plain steel rod, with a hole drilled at one end in the direction of the axis, are the best. Those that are perforated transversely like the lanterns of screw-point tools, do not produce such good riveting, since the parts of the end, from behind which metal has been removed, are more or less elastic.

=246.= =Burnishers.= Burnishers will not remain in good condition unless their surfaces are prepared, from time to time; in the case of those used for very fine work, by passing over a buffstick charged with polishing rouge or very fine emery, and other kinds on an emery stick more or less fine, according to the degree of roughness the burnisher is required to possess.

=247.= _To re-face a burnisher._ Pivot burnishers are usually re-faced by a lapidary; a watchmaker can, however, do it for himself very effectually in the following manner: Prepare a dry, smooth piece of wood, rather thick, and of a width equal to the length of the burnisher. On this board carefully glue a piece of emery paper, of a fineness corresponding to the degree of cut required, stretching it as even as possible, and turning the edges down towards the under side. Then lay the board on a firm smooth surface, resting a weight upon it, and allow it to dry.

In using this lap, it is fixed or allowed to rest against the side of the bench; holding the burnisher with two hands at its extremities, the workman places himself at one end of the board, and draws the burnisher along it towards him, maintaining the surface quite flat and applying considerable pressure. On reaching the nearer end, raise it, and after again placing it on the farther end, draw towards the body, and so on.

By proceeding in this manner and always in the same direction, placing the burnisher so that the acting edge is farthest away from the operator, all risk of rounding this angle will be avoided.

=248.= =Broaches.= Great care is needed in adapting handles to broaches. Resting the point against a finger of one hand and causing the handle to rotate by two fingers of the other hand, the broach itself should be seen to remain true.

It is a good precaution, suggested by M. H. Robert, to gently draw a piece of iron, charged with rouge, along the edges of pivot broaches in order to remove the thread of metal from them. Minute particles of this thread would otherwise remain in the holes, and occasion wear of the pivots.

These fine broaches are not fixed in handles, but a piece of sealing-wax is melted on to the upper end; then, holding the broach between the fingers, with its stem downwards, it is rotated while held to a flame, so that the sealing-wax forms a regular, oblong handle.

=249.= =Blow-pipes.= In order that a long even flame may be obtained, the hole should be of moderate size and perfectly clean around the edge; otherwise the jet cannot be straight and sharp. Difficulty will always be experienced by anyone who has not learned to breathe without interrupting the continuity of the blast. Where a supply of gas is available, the gas blow-pipe presents advantages from the point of view of convenience.

[Illustration: _Fig. 52._]

Fig. 52 shows a gas blow-pipe for jewelers, which is simple and convenient. It consists of a blow-pipe of the ordinary form, having a gas pipe inserted in the lower half, and a threaded hood or sleeve at the lower end, which changes the shape of the flame by screwing in or out, so as to vary the influence of the current of air upon the flame. A ring adapted to slip over the finger while working, is soldered to the middle joint of the pipe, and the quantity of gas is controlled by the stop-cock and spring lever shown in the cut, the gas being supplied to the pipe by a rubber tube connecting it to the nearest gas jet in the usual way. Thus having the shape of the flame under control and the quantity variable at will, the workman is in position to accomplish the desired end speedily and effectually.

To use to the best advantage, set the jamb-nut so that with the valve lever in its normal position, the flame at the end of the pipe will just keep alight. The blow-pipe can then be laid down temporarily and again used without the trouble of turning off the gas or relighting.

When used as a mouth blow-pipe, the most convenient way to hold it is with the third finger through the ring. For bellows work it is better to pass the ring over the index finger. The ring also serves, with the valve-lever, as a rest to hold the flame-nozzle away from the table when the blow-pipe is laid down temporarily.

To produce an oxy-hydrogen flame, connect the air-pipe with a cylinder of nitrous oxide, opening the cylinder-valve carefully, so as to permit the escape of only sufficient nitrous oxide to produce with the illuminating gas a very small flame. Regulate the illuminating gas flow with the thumb-screw or with the finger on the lever of the blow-pipe valve.

[Illustration: _Fig. 53._]

Fig. 53 shows an automatic hand blow-pipe for use with a foot blower. One of the rubber tubes shown is connected with the blower and the other to the gas supply. It is self adjusting for both gas and air, requiring only a slight motion of the lever, shown under the thumb, to obtain instantly any flame, from the smallest to the largest; so that these pipes have all the delicacy of the best mouth blow-pipe, used with the utmost skill, together with the power and advantages obtained with a mechanical blower.

=250.= =Small gas furnaces.= The workman will frequently have occasion to anneal pieces of steel or to raise to a red heat objects that are too large for the blow-pipe; an ordinary open fire aided by bellows is often resorted to in such a case. A better plan, however, is to use any small portable gas furnace, provided with a hood that completely closes it at the top.

Fig. 54 shows a gas melting furnace, which is kept by material and supply houses. It is powerful enough to melt gold, silver, brass and copper, but is not recommended for cast iron. It can be used for scorifying and cupelling. The lid can be pushed sideways sufficiently to give access to the interior of the furnace.

[Illustration: _Fig. 54._]

The following points in the management of a gas furnace will be of service to all novices in their use. The power and speed are practically without limit, depending only on the gas and air supply, and are under perfect control. Allowing five cubic feet of gas for heating up, it requires about four feet of gas for every pound of cast iron melted. For small work it is as cheap as a coke furnace, and not one-quarter the trouble.

The quantity of air required depends upon the gas supply. One must be equal to the other, so that perfect combustion will take place, and that entirely within the furnace. An excess of either gas or air renders a high temperature an impossibility.

See that all gas taps have a large clear way through. High temperatures and rapid working require a free supply of gas.

To adjust a new furnace to its highest power, connect both gas and air supply with the burner. Turn on the full gas supply, light the gas, the air-way being full open, work the foot blower and then put the gauze nozzle of the burner tight against the hole in the casing, so that no flame escapes around it. If the flame comes out of the lid about two inches, the adjustment is right. If the flame is longer, open the air check until the proper flame is obtained, or reduce the gas supply. If smaller, or not visible, close the air check until the flame appears.

The cap-nut, which will be found at the throat of the horizontal “mixing tube,” where the air enters and mixes with the gas, is used for changing the size of the orifice from which the gas escapes. When the escape is from a large orifice, a smoky, yellow, or “reducing” flame is the result. By contracting the orifice by screwing the cap-nut on to the gas delivery tube, a blue or oxidizing flame will be obtained. Adjustment for the proper flame should first be made by this nut, and the size of the flame regulated afterwards by means of a cock at the gas main. A slightly yellow flame gives the best results when a high heat is desired. The arrangement above described is clearly shown at the left-hand lower corner of the sectional illustration above.

A chimney or stove-pipe 8 or 10 feet high may be used as a fixture, and the draft partially stopped by the damper or slide when lower temperatures are required, the gas being turned down in proportion; the guide for the proper adjustment being that UNDER ALL CIRCUMSTANCES THE FLAME MUST JUST COVER THE CRUCIBLE OR MUFFLE, but not extend into the chimney so as to make it red hot. When the flame covers the crucible or muffle, the gas is doing its extreme duty under the most favorable circumstances, without waste.

Keep all fluxes away from the furnace jacket, as they are injurious to fire clay, and are liable to cause the lids, etc., to stick to the furnace.

A thin layer of quick lime on the bottom of the furnace will prevent the crucible adhering to it when very hot.

When using a furnace for high temperatures, care should be taken not to use a fire clay casing, as it melts at a temperature a little above that of cast iron; plumbago or asbestos only should be used when very high temperatures are required.

[Illustration: _Fig. 55._]

Fig. 55 represents a small gas furnace, which is extremely useful for small meltings, experimental work, etc. It consists of a pot made of a mixture of fire clay and asbestos, bound with rivetted iron hoops, and having a hole in the side at which the flame enters. A lid pierced by a central hole permits the escape of the products of combustion, and the crucible is placed in the center so that the flame surrounds it. It is worked with gas and a foot blower. Gas from a ⅜-inch supply pipe will work it efficiently. About ten cubic feet of gas per hour is sufficient for most purposes.

The casing holds the heat so perfectly that the most refractory substances can be fused with ease, using a Fletcher foot blower. Half a pound of cast iron requires from seven to twelve minutes for perfect fusion; the time depending on the gas supply and pressure of air from the foot blower. The crucible will hold about ten ounces of gold.

The power which can be obtained is far beyond what is required for most purposes, and is limited only by the fusibility of the crucible and casing.

[Illustration: _Fig. 56._]

Fig. 56 represents a small apparatus, which, owing to its speed and economy of operation, has a very extended use in the jewelry and silversmithing trades. With this apparatus a sound two-ounce ingot of gold or silver can be moulded in two minutes. A crucible of moulded carbon is supported by a sheet-iron slide, or plate, which is clamped to an ingot mould by a clamp which swivels in the U-shaped cast iron stand. The metal to be melted is placed in the crucible, and the flame of the blow-pipe directed on it until it is perfectly fused. The whole is then tilted over by means of the upright handle at the back of the mould. The waste heat serves to make the ingot mould hot. No flux should be used with the carbon crucibles. For the smaller operations, such as making small quantities of colored golds, for electroplating solutions, testing ingots, and the smaller operations of the jeweler and plater, it is invaluable.

[Illustration: _Fig. 57._]

The air pressure used in operating gas furnaces varies from one to four pounds per square inch, though the latter is seldom required except for the severest work in large furnaces; as a general rule it is less than two pounds in the operations of the gold and silversmith. The pressure must be arranged so that the air supply equals that of the gas used. This can be readily seen by the color of the flame, as noted in instructions for handling the furnaces. For small operations foot blowers are used. These consist of a powerful bellows having a hemispherical pressure chamber on one side, and adapted to work either by the hand or foot; see Fig. 57.

[Illustration: _Fig. 58._]

[Illustration: _Fig. 59._]

The perfect combustion of the gas is secured by mingling equal quantities of gas and air in a mixing chamber, and then igniting the mixture. In the larger furnaces this is accomplished by a mixing chamber placed under the furnace, so as to heat the mixture before ignition, and no pressure supply of air is necessary. In the smaller apparatus, this mixing is done in the burner, which consists of an inner tube carrying an air supply, surrounded by a gas tube, and the whole surmounted by a sliding nozzle for changing the shape of the flame. The mixing chamber being so small, the air and gas pass through it so rapidly that considerable pressure of air must be provided to prevent it from being excluded by the normal pressure of the gas; hence the necessity for a blower when using small burners.

When it is not desirable to use gas, for pecuniary, or other reasons, melting may be carried on by means of a gasoline gas flame, which is noisy, but otherwise little inferior to coal gas. The furnaces for gasoline differ but little in construction from the others, as will be seen by Figs. 58 and 59. The only difference being that the burners are applied from the side and no air pressure tubes are needed, while the furnace is supported on legs to insure safety from fire.

[Illustration: _Fig. 60._]

The burner for gasoline is radically different from that for gas, being, in fact, a small gas machine, Fig. 60.

In Fig. 60 _P_ is an ordinary force pump, at the bottom of which, at _A_, is a valve which closes automatically upon releasing the pressure from the pump, _C_ is a check valve which closes the inlet to the tank _T_ completely; _F_ is a filling screw for introducing gasoline. _V_ is a vent screw for letting off the pressure when through; _H_ is a pipe leading from the tank to the burner _D_; _E_ is the burner regulator, terminating in a fine point, closing the orifice of the burner; _S_ _S_ are packing boxes. Upon opening _C_ and pumping a few strokes a pressure is created in the tank and on top of the fluid, forcing it through the tubes of the burner, which being previously heated, vaporizes the gasoline. This issues from the orifice at the end of _E_ as a highly heated gas and burns as such in the form of a powerful blast, Fig. 61. After being once started the heat of the flame passing through the burner, vaporizes the fluid in the tubes, and hence the apparatus is automatic.

[Illustration: _Fig. 61._]

The air which is forced in is not consumed, so that to keep up the blast it only requires a few strokes of the pump occasionally to maintain the pressure lessened by the consumption of the fluid.

To operate the blow-pipe: close _E_; unscrew _F_, and introduce from two quarts to one gallon of gasoline of 76° according to the capacity of the tank. Replace _F_ and close _V_; open _C_ one or two turns and give three or four full strokes of pump _P_, and close _C_. Heat the burner by burning some of the fluid in a suitable vessel placed under the burner; when hot enough apply a match and open _E_ gradually, until the action is more or less uniform. If no spray or liquid issues from the orifice, the burner is hot enough; if not hot enough, burn slowly until no liquid or spray issues. When sufficiently heated the blast can be made of any intensity desired, by the use of the pump as above. To stop its action, shut the regulator _E_, or open screw _V_, or both. When not in use the vent _V_ should invariably be kept open. The mouth of the burner _D_, should be two or three inches from the inlet of the furnace, or there will not be perfect combustion.

For very high temperatures and muffle work, light the burner as above and heat the inside of the furnace to a bright red; then place the burner against the inlet of the furnace; turn out the burner by means of the cock _E_, and immediately turn it on again without lighting it, when if the furnace is hot enough, the gas will ignite inside the furnace. The heat can be regulated as in the first method of burning. When burning inside of the furnace, there must be no flame in the burner tube; it should all be inside the furnace, and the tube of the burner must be close to the fire hole, or there will not be enough heat in the tubes.

Use a drop or two of sperm oil on the piston of the pump occasionally, also on leather washer at _F_, otherwise the apparatus will be apt to leak, corrode and work badly.

[Illustration: _Fig. 62._]

=251.= =Muffle Furnace.= This consists of a fire-clay furnace, mounted upon a powerful gas burner and containing an oven, also of fire-clay or plumbago, so placed as to receive the full heat of the flame, without permitting the direct action of the flame upon any object placed within it. The objects are placed in and withdrawn from the muffle, or oven, through the door shown in the cut. This door is made of two pieces so that the upper one may be removed to watch the progress of the work without chilling the contents of the muffle by too great an entrance of cold air. They are extensively used for assaying, annealing, etc., and for many other purposes where an exact temperature is required. The illustration shown in Fig. 62, is of a gas muffle, but they are also made to be used with the gasoline burner previously described.

THE LATHE.

=252.= Of all the tools and machinery employed by the watchmaker, the lathe is the most important. Very poor work is often turned out by those possessing a first-class lathe, but there are very few persons who can turn out good, true work, from a poor, cheap lathe, and if it is untrue it is utterly impossible to turn out good work. Wonders can be accomplished by the ingenious mechanic who thoroughly understands the capabilities of the lathe. By patient skill of manipulation, the Chinese and Japanese turn out some truly wonderful work; they succeed in turning sphere after sphere, one inside the other, from a solid piece of ivory, the opening from one to another being comparatively small.

The earliest form of the lathe in the trade was the dead center: that is, a lathe whose parts did not revolve, the object to be operated on being placed between centers and made to revolve by means of the bow. This form of lathe was succeeded by the live spindle or live mandril pattern, although there were many good points about it that must be acknowledged. It contained one great element that many modern appliances, termed lathes, lack, i. e., the element of truth. No matter how coarsely or crudely constructed, this truth was not eliminated, except by the ignorance of the artisan, for the centers must remain the same relatively, whatever may be their position in relation to the lathe bed.

With the introduction of the live spindle lathe in this country, the verge, Jacot and other lathes and tools of that type were rapidly abandoned. In Europe, however, the live spindle lathe did not meet with such a cordial reception, and it has taken many years, in some localities, to overcome the prejudice against them; in fact, there are still many workmen there who cling to the dead center patterns.

The all-important point in lathes of the live spindle type is accuracy of fitting, and particularly in regard to the spindle and its bearings, for unless a certain degree of perfection is attainable in this particular, it is worse than useless, as it not only does not do the work, but leads the artisan astray. The workman, sometimes, through motives of economy, purchases foreign made lathes, that closely resemble the American in outline and finish. These lathes, as a usual thing, are not accurate, and in the greater majority of cases the chucks which accompany them are worse than nothing, and yet these lathes, in nearly all cases, are declared to be as good as the American. There are some foreign lathes that are very carefully made, and are quite as true as the best American, but they are the exception and not the rule. The workman who buys one of these lathes cannot, of course, tell whether it is right or wrong until he has placed it on his bench and tested it, and even then he cannot be sure, for although when a certain chuck is placed in the spindle and tested it may apparently show no deviation from truth, there may still be untruth in the spindle or chuck or both, as the errors in one may be counteracting the errors in the other, and if the chuck be turned or an absolutely true chuck placed in the spindle, the error will be made quite apparent. If an American lathe, by any possibility, is allowed to pass the inspector, and finds its way upon the market, the maker is only too glad to replace it with a perfect one, for his reputation is at stake; but if one of the imitation pattern proves untrue you will have to do the best you can.

[Illustration: _Fig. 63._]

There are American made lathes upon the market that are as inferior in many respects as the imitations, and the watchmaker will do well to do without a lathe until such time as he can afford to purchase one of known reputation. Among the first-class American lathes upon the market may be mentioned the Webster-Whitcomb, shown in Fig. 63; the Moseley, shown in Fig. 64; the Hopkins, shown in Fig. 65, and the Rivett, shown in Fig. 66, and others.

An excellent lathe for the heavier work of watchmakers and jewelers, such as cannot be performed with satisfaction on the watchmaker’s lathe, is the No. 4 Barnes, which is shown in Fig. 67.

[Illustration: _Fig. 64._]

For screw-cutting, the manufacture of watchmaker’s tools, fishing reels, repairs on tower clocks, in fact, all the heavier work of the trade, it is admirably fitted.

=253.= =Care of the Lathe.= The American lathe of to-day is a marvel of completeness in its parts, and how many hours, yea months, of study and experiment have been bestowed upon it by its projectors and makers to acquire these points of utility and excellency? What a vast amount of care has been exercised for the production of a perfect lathe! Must this care cease at the moment it passes into the hands of the watchmaker?

It is a very easy matter at any time to wipe off the dust and oil that may accumulate, but does this alone constitute due care? There may be a nice glass case to cover it and keep off the dust, and a very good idea it is, if faithfully used; but if a counter shaft is on the bench, or much lathe work is to be done, it soon falls into blissful desuetude, or finishes its usefulness by being broken. Then, often, a cloth is wrapped about the lathe, which soon gets soiled and looks badly, let alone the poor protection it affords.

[Illustration: _Fig. 65._]

Dust is omnipresent, and the greatest enemy to all active machinery; it insidiously makes its way into every crease and crevice, and if not promptly removed will cause untold damage. We cannot get rid of it and must (like the industrious housewife) wage a constant warfare against it.

The care necessary to be given to a fine lathe differs from most other tools; it is not confined alone to the removal of dust and keeping clean, but the fitting properly of the several parts as used. There should be no overstraining when tightening screws, chucks, etc., or when fitting articles in both wire and wheel chucks, and so on through the list.

[Illustration: _Fig. 66._]

The face of the lathe bed when it comes from the makers is (or should be) perfectly true from end to end, in order that head and tail stocks will meet on a direct line of centers, even should they be changed end for end, and a good lathe will meet those requirements. Now, it is obvious to any thinking mind that if this face becomes injured by neglect, whereby the nickeling is removed in spots or portions, they will, in all probability, become rusty; this rust will then eat away and throw off more, and soon the face presents an uneven surface, which will tend to destroy the line of centers between head and tail stocks.

The head stock, usually occupying one position, causes less wear at this point or place, while the hand-rest and tail stock are constantly being shifted, so where there is more motion or action there must be more wear, especially if dust, chips, or grit be allowed to accumulate beneath them, and though the wear is seemingly imperceptible, it nevertheless is there, and will sooner or later manifest itself, and this is a signal that the level of the bed is becoming impaired, and, necessarily, the truth. Thus too much care and attention cannot be exercised in guarding against chips and dust when sliding hand-rest back and forth on the bed.

[Illustration: _Fig. 67._]

At the end of the bed, where the tail stock takes position, many watchmakers have the tail stock off, and this portion is more exposed to atmospheric action, also receiving perspiration from the hands when they come in contact. Again, others let the tail stock remain in position, only removing when it comes in the way. In the former case, it is well to devise some means for the protection of the bed; this is easily done by making a sheath of chamois skin to slip tightly over the bed; it can be removed and replaced readily, and when it becomes soiled, can be washed.

This sheath should be fully two-thirds the length of bed, or reaching from tail end up to hand-rest when it is close to head stock. It preserves the bed from dampness, which is considerable in some climates, also the perspiration of the hand and flying chips and dust. In the second case, if the tail stock is allowed to remain on the lathe, or, if removed and placed on the bench, it is subjected to all the evils the bed is in the former. Our opinion is, the tail stock should be kept in its compartment in a tight-fitting drawer, away from dust and accidental knocks of other tools on the bench; the tail spindle not being nickeled, is more liable to rust if left exposed, and should be kept in a sheath of oiled paper. This may seem superfluous and too much bother, yet it is taking proper care which tells in the end.

The bottom of tail stock should always be brushed off before placing in position, not only for its protection, but for fear some particle of grit may be adhering, thereby throwing it out of truth, and screwing it down tight only adds injury to the lathe if allowed to remain.

The head stock demands close attention; the spindle should run freely without end-shake, and about once a week should be speeded, meanwhile administering oil until it leaves the bearings clean, and then wiped off. A little oil should be added every day. See that the mouth of the spindle is kept bright and clean; thrust a piece of cloth clear through spindle every now and then, that all dust and dirt may be removed.

Wire and wheel chucks should often be washed in gasoline to remove gummy dirt and oil which is constantly adhering, and it is even well each time a chuck is used, to wash off first, then wipe dry. A little dirt on the mouth of spindle, or on the chuck, often throws it out of truth, and consequently the article fastened therein also.

When fitting head or tail stocks, or in fact any attachment, do so carefully. Do not bang it in place as if you held a grudge against it, and when in position see that they are tightly screwed in place.

Having too much end-shake on live spindle, especially in soft lathes, causes uneven wear in its bearings, besides not being reliable for true pivoting or any such work.

When the cost of a lathe is taken into consideration, it goes to prove that it is not easily replaced. Where is the jeweler with a stock of goods who would retire without first seeing that his valuables were in the safe, but how many are there that think of giving this protection to their lathes? Some do, but the greater per cent do not. It is a good plan to see that the head stock, the tail stock, and attachments are in the safe and should a fire break out that endangers the store, and no chance to save it, the feeling of satisfaction is great to know the lathe is safe, that is, the most expensive parts, for the bed can be purchased at a nominal cost compared to the attachments.

THE FOOT WHEEL.

[Illustration: _Fig. 68._]

=254.= In the selection of a foot-wheel the workman must be governed by his own experience and taste, for the variety that exactly suits one person is very distasteful to another. The swing treadle pattern shown in Fig. 68 is a very popular one with American workmen. These swing treadles are made in various ways by the different manufacturers, but the methods of using them are alike. There are workmen, however, who prefer the heel and toe motion and others that prefer the up and down motion. This is all a matter of taste and it matters but little what form of lathe wheel is used provided the motion is steady and the exertion is light. As a general rule a heavy wheel, say forty pounds in weight, will be found, on the whole, much better than a light one and the motion will be more uniform.

=255.= =Driving Bands and Belts.= Most foot-wheels are so constructed that either a flat or round belt may be used in transmitting the power to the countershaft or lathe, as the case may be. Many watchmakers use a flat belt between foot-wheel and countershaft and a round leather belt, or cord, between countershaft and lathe. If we may judge by appearances, this is the favorite fitting. Others use round leather belts in both instances, while others again use cotton or hemp cord or gut. All things considered, the round leather belt seems to possess advantages over all others. It does not slip as easily as cotton cord, is more elastic than gut and throws less strain on the bearings, absorbs less power and works much smoother. The ends are fastened together by means of an S hook and the cord may be readily tightened by giving it an additional twist or two.

[Illustration: _Fig. 69._]

=256.= =The Countershaft.= The countershaft is indispensable in using milling tools, wheel cutters and pivot polishers. The pattern shown in Fig. 69 is but one of many on the market.

In some of the patterns the uprights extend through the top of the bench and are held securely in place by means of thumb screws or wing nuts. The pattern shown in the illustration is mounted on a solid metal base which is intended to be fastened to the bench by means of screws. The advantages of using a countershaft are three fold: First, you are able to regulate your speed perfectly without changing the motion of the foot from fast to slow or vice versa; second, your belt is carried to the back of the bench, where it is out of the way, instead of coming down in front of the head; and third, you obviate the necessity of having holes in your bench on each side of the lathe, that small articles are liable to drop through. Fig. 70 illustrates the favorite arrangement of foot wheel, countershaft and belts.

THE BENCH.

[Illustration: _Fig. 70._]

=257.= As previously suggested (=230=) it is of the utmost importance in doing good work, and doing it rapidly, that your bench be kept orderly and clean at all times, and that all your tools and devices be in their proper places, exactly where you can put your hand on them at a moment’s notice. An excellent arrangement for a watchmaker’s bench is shown in Fig. 70. This bench was designed by G. W. Laughlin, and is complete in every detail. Benches can be purchased ready made from material dealers, both with and without curtain tops, but there are many watchmakers that prefer to make, or have made for them, a bench varying from the usual pattern. The bench illustrated is made of black walnut, veneered with French walnut and bird’s eye maple. The top is 21 inches wide by 41 long and is 33 inches from the floor. The drawers on the right-hand side are 10 inches wide. In the center are two shallow drawers, while the left-hand side is entirely boxed in.

IDLERS.

[Illustration: _Fig. 71._]

[Illustration: _Fig. 72._]

[Illustration: _Fig. 73._]

=258.= Idlers are especially valuable for use on slide rest tools, such as pivot polishers, milling attachments, wheel cutters, etc., and with traverse spindle tailstocks, traverse spindle drivers, etc., to give a vertical direction to the belts. Idlers are constructed in various forms, some of them being mounted on upright posts, fastened to the bench just back of the lathe, as shown in Fig. 71; others consist of steel rods terminating in a ball, and socket joint, where it is fastened to the bench, as shown in Fig. 72, while in other patterns the rod is fastened by means of a wing nut to a brace running from one to the other of the supports of the countershaft and may be placed at any desired angle. The idler shown in Fig. 73 can be used in this way. Some watchmakers prefer to place their idlers on an overhead countershaft, which is usually fastened just back of the bench and about two and a half or three feet above it. The idler shown in Fig. 72 can be screwed to the bench or to the wall above the bench, in the latter case it will extend out horizontally over the lathe and is out of the way of the watchmaker when not in use. In the forms shown in Figs 71, 72 and 73 the belt passes from the countershaft over the idler and one long belt only is used. This style is sometimes varied by using two separate belts one from the countershaft to the idler and another from the idler down to the lathe. If in the latter style, a cone pulley of rubber is used on the countershaft and also for the corresponding pulley on the idler and a plain pulley for the down belt. Of course in this form the idler stand must be in the form of a countershaft, as the pulley must be fast on the shaft and the shaft itself must revolve. In the styles shown above, the shaft is rigid and the pulleys revolve upon it. The advantage of using the cone pulley style is that the speed of the cutter or other attachment may be varied at will without in any way increasing or decreasing the speed of the wheel.

CHUCKS.

[Illustration: _Fig. 74._]

[Illustration: _Fig. 75._]

[Illustration: _Fig. 76._]

[Illustration: _Fig. 77._]

[Illustration: _Fig. 78._]

[Illustration: _Fig. 79._]

=259.= True chucks are the most important adjuncts to a watchmaker’s outfit. A true lathe with poor, untrue chucks is almost useless. Chucks hold the work truest that comes the nearest to fitting the holes in them. If you try to hold work in a chuck that is too large or too small, you will soon get the chucks out of true and you will soon become dissatisfied with your chucks, your work and your lathe. Care should always be taken to select a chuck that will take the work without straining it open and yet is not so large that undue pressure will have to be used in holding it. The American split chuck, when true, will hold almost any piece of work with the greatest precision as regards truth; but the split chuck is a delicate attachment and will not stand hard knocks and rough treatment. After using them, you should clean them in benzine to remove all dirt, rinsing them in alcohol and drying with a soft linen rag, and see that no small chips of metal are left in the openings that may throw the work out of truth the next time they are used. Fig. 74 illustrates the regular pattern split chucks that accompany American lathes. Fig. 75 is a conoidal wire chuck, so called because the shape of the mouth of the chuck is conoidal in lieu of the shoulder usually left on wire chucks for the bend in the spindle. Fig. 76 is an arbor chuck. This is a solid chuck on the end of which is a threaded arbor for the reception of saws, laps, wheels, etc., which are held firmly in position by means of the nut on the threaded arbor. Fig. 77 is a screw chuck. This is a solid steel chuck having a threaded hole in the end for the reception of cement brasses, etc. Fig. 78 is a shoulder chuck. It is a split chuck with a large opening in the end with square shoulders for the work to rest upon. Fig. 79 is a taper chuck, which is solid and has a large opening for the reception of tapers, centers, laps, etc. Fig. 80 is a step or wheel chuck, which usually comes in sets of five, and as each chuck has nine steps, a set of them will accommodate forty-five different sizes of work. These chucks are useful for holding mainspring barrels when fitting in the cap, should it become out of true; for trueing up the barrel of English lever watches that are damaged by the breaking of a mainspring and for holding almost any wheel in a watch, such as the fitting of a center wheel to a pinion, or in making sure that hole in the wheel is in the center. These chucks will the hold wheels from 5 to 2.25. The chucks mentioned above are the most common ones in every day use and usually accompany the American lathe in combination sets. As intimated, these chucks are delicate and as a usual thing they do not receive the care they should, when their cost and the delicate exactitude demanded of them is considered. The watchmaker who prides himself on his good work and the orderly condition of his tools, attachments and bench generally will purchase or make for himself a nice chuck box with a glass or wooden cover to exclude all dust and flying chips. You cannot expect to do good true work with a chuck that is thrown carelessly into a drawer containing an assortment of files, a hammer, staking block, oilstone, screw driver, sliding tongs, etc., and yet how many watchmakers take just this kind of care of their chucks, and complain of their untruth, and declare that a wax chuck is the only thing that can be absolutely relied upon for truth. Fig. 81 illustrates a neatly arranged chuck box made by the Faneuil Watch Tool Company. In it all the various chucks may be arranged and the whole may be covered with a glass shade to keep out all dirt. A wooden cover might be used and perhaps would be preferable to many as it is less liable to be broken and occupies less space and therefore admits of the box being placed in a drawer, leaving more room on the bench for the necessary tools and attachments.

[Illustration: _Fig. 80._]

[Illustration: _Fig. 81._]

A chuck box should be well soaked in oil so that the wood will absorb no moisture and thus tend to rust the chucks. A small envelope made of tissue paper and filled with quicklime will, if placed in the chuck box, take up the moisture in the air and prevent the chucks from rusting.

[Illustration: _Fig. 82._]

=260.= The chuck stepping device, invented and patented by Mr. Moseley, is a valuable attachment for the lathe. In this device, shown in Fig. 82, _a_ rests in chuck slightly less than diameter of work; _b_ tightens in rear end of draw-in spindle, and turning _c_ regulates the depth of step. By the use of this tool any wire chuck will accurately serve as a step chuck. It is a device of great service to the watchmaker when used and understood. It enables him to make a step in any wire chuck of any depth he may desire, and will push out the work at any time when he so desires. It is very useful many times for a stop for marking or cutting off when you want a number of pieces of the same length or kind. Many object to the stepped chuck for general use.

[Illustration: _Fig. 83._]

=261.= In addition to the regular chucks which usually accompany American lathe combinations may be mentioned some others which from time to time have been placed upon the market by manufacturers of watchmakers’ tools. These chucks were devised for holding work which it was found in practice could not be held by the ordinary chucks.

=262.= The bezel chuck, shown in Fig. 83, was originally made with a view of holding bezels only, but is now made so that it will hold watch plates, coins, etc., and is adjustable to any size. It can be fitted to any lathe and it requires but very little practice to use it, as it is extremely simple and any one who uses a lathe can make or repair bezels in a workmanlike manner. It holds the work as in a vise, and no amount of turning or jarring will loosen the jaws, while it may be opened or closed instantly by simply turning the milled nut behind the face plate, thus enabling the operator to turn and fit a bezel perfectly, by trying on the case as many times as necessary. It holds the bezel by either groove, so that the recess may be turned out when too shallow or too small for the glass, or the bezel may be inverted and turned down when it rests too hard against the dial. It will be found especially useful in turning out the inevitable lump of solder from the recess of the bezel after soldering, and in fitting to case, as the process of soldering generally makes the bezel shorter, and consequently it will not fit the case. It also renders the operation of polishing bezels, after soldering, the work of but a few moments. In turning out the recess for glass in bezels, especially those of the heavy nickel variety, it will prove a friend indeed. When, for instance, you look through your stock of flat glasses and find none to fit, but have one that is just too large. Any watchmaker knows that if the groove in the bezel is imperfect, it is very apt to break the glass. This chuck is also useful as a barrel closer, holding work while engraving, and many other uses that will present themselves to the watchmaker.

[Illustration: _Fig. 84._]

=263.= The Hopkins’ patent adjustable chuck, shown in Fig. 84, is designed to grip and hold firmly and accurately any size of work, from the smallest staff to the largest pinion, watch wheels of all sizes, mainspring barrels and other large work, and can be adjusted to any make of lathe, by simply placing it friction tight on a plug chuck fitted properly to the lathe. In using this chuck for staffs, pinions, wire, etc., fasten a V-piece, 7, of proper size, in the hole of attachment 6, taking care that both the V and the seat in which it rests, are free from chips, dirt, etc. Then lay your work in the V and fasten it there by means of the sliding jaw above it. This done, place the attachment on the face of the chuck body, with the disc slipped under the heads of the two spring bolts, and then spin the work to center the same as when using wax. After centering thus, fasten the disc to place by tightening the nuts on the back ends of the spring bolts. For holding work by the web of the wheel, place the wheel under the screw cap, on the face attachment 8, and screw the cap down firmly on it, with the staff or pinion projecting outward through the center hole. This done, proceed the same as when using attachment 6. For mainspring barrels and like work, use attachment 11, and place a bit of broken mainspring between the work and the ends of the three binding screws, and tighten the screws down on this instead of directly on the work.

[Illustration: _Fig. 85._]

[Illustration: _Fig. 86._]

=264.= The Spickerman patent cement chuck, shown in Figs. 85 and 86, holds and centers accurately any wheel in a watch while drilling, polishing or fitting new staffs or pinions, and all danger of injuring the wheels is obviated. It will fit all kinds of American or Swiss lathes. The holder shown in Fig. 86 at _a_, is turned down to nearly the size of the screw for the lathe, and the screw is cut so the holder will set as close as possible to the lathe. The face of the holder is then turned perfectly true. Put the wheel to be centered in cap _c_, as near to the center as convenient, and then screw on _b_. Then place the cemented face of chuck _b_ against the face of holder _a_ on the lathe, and with a lamp warm the cement between the surfaces, holding the chuck by means of a pegwood against the pivot of the wheel in the cap _c_, and it will move to an exact center as soon as warmed sufficiently. New cement should be added occasionally between the surfaces, as the old cement hardens and burns away, and does not center as well as when new. Fig. 85 shows chuck with wheel inside ready for centering and drilling.

[Illustration: _Fig. 87._]

[Illustration: _Fig. 88._]

=265.= The gem patent pivoting chuck, shown in Figs. 87 and 88, is intended as a substitute for wax when performing pivoting and like work. By the means of the ball _b_, placed between the two sliding sockets _c_, _c_, with the several other parts as represented in Fig. 87, a combination of sliding and ball and socket movements, in connection with a spring pump-center is obtained. A set of ten or more supplementary chucks _g_, with different sizes of center holes, and attachment _n_ for all sizes of wheels, are furnished with each chuck. The supplementary chuck _g_, in the form of a small split chuck, is made to fit into a hole with taper mouth, in the center of the ball _b_, and is drawn into place and the work fastened firmly in it by means of the binding nut _m_, which screws on to a projection extending outward from the front of the ball. To use this chuck, proceed as follows: Remove the nut _m_, and give freedom to the working parts by loosening the large back nut _k_. Then to bring the hole through the ball _b_ into line, spin the ball to center, first at the base of the projecting screw and then at the mouth of the hole through it, and in this position again fasten the parts, by tightening the nut _k_. Then give freedom to the pump-center by slightly loosening the set screw _j_. When doing this, hold your finger against the front of the chuck, to prevent the center rod from shooting out of its place when freed. Then having placed a supplementary chuck _g_, of proper size, in its place in the chuck, and your work in it, with its back end resting properly in the countersink in the end of the pump-center, fasten it there by screwing the cap _m_ down snugly over it, using a small lever pin when necessary for the purpose, but not with undue force. Then again loosen the nut _k_, and spin the work to center at its outer end; and then tighten both the nut _k_ and set screw _j_. In tightening the set screw _j_, make sure it is so tightened as to prevent the pump-center from slipping from place when working. If from tightening the screw _j_, it is found that the work has been thrown in any degree away from true center, loosen the nut _k_, leaving the pump-center fast, and again spin to center and fasten as before. After a little practice this can all be done in a few seconds, and the work brought to absolute center.

In using attachment _n_, for wheels, the nut _m_ and chuck _g_ are removed, and n is substituted therefor; the work being held on the face of the attachment by flat-headed screws that grip the arms of the wheel. For cylinder escape wheels a special attachment _n_ is furnished.

[Illustration: _Fig. 89._]

[Illustration: _Fig. 90._]

=266.= Fig. 89 illustrates a crown chuck, which is used for holding crowns while undergoing repairs. The Dale chuck shown in Fig. 89 is made on the lines of the ordinary split wire chuck, a large recess being turned in the end for the reception of the crown. The Johanson chuck is illustrated in Fig. 90, and is quite different in construction, a ball-shaped cap with right hand thread screwing down onto the body of the chuck, thus holding the crown from the outside, while a screw-center with left hand thread, holds it firmly from the inside. This chuck is made in two patterns, one for use in a No. 40 wire chuck, as shown in Fig. 90, and the other is mounted on a regular chuck and is ready to insert into the lathe-head the same as an ordinary wire chuck.

THE SLIDE REST.

[Illustration: _Fig. 91._]

=267.= The slide rest is an expensive but very useful adjunct to the lathe. It is used so extensively in this country, however, that a full description of it seems superfluous. Fig. 91 is a fair example of a modern slide rest for the American lathe. The tool-holder varies with the different makers, but the rests proper are all made on the same general principles, that of two sliding beds working at right angles to each other, and carrying a tool-holder, capable of being raised or lowered or set at any desired angle.

=268.= Brass is easily turned with the slide-rest in an ordinary lathe arranged for the purpose, but the turning of steel demands more care in setting the cutter so as to obtain the best cutting edge as well as in determining the point of application of the tool. Preliminary trials must be made, and the following remarks will be of service as a guide.

[Illustration: _Fig. 92._]

=269.= Engineers use a hooked tool to a very great extent for both planing and turning. Both experience and reasoning point to the conclusion that a tool of the form _b_ or _d_ Fig. 92, possesses many recommendations, and numerous designs of hooked tools more or less resembling these figures are employed with advantage; the tool occupies the best possible position in reference to the surface it is required to cut, and the cutting edge is both sharp and solid. It will be evident that a certain relation exists between the cutting angle and the point of application of the tool to the cylindrical object that is being turned, and this it is necessary to determine. With a hooked tool, as with the ordinary slide-rest cutter, a cutting angle which is too acute will wear away rapidly; when too obtuse, the tool scrapes and will only act when considerable pressure is applied.

In conclusion, it is clear that in forming or re-grinding any tool for cutting a surface, it must be so arranged that its edge makes the least possible angle with the surface that is consistent with the securing of a sufficient degree of resistance to the cohesion and the hardness of metal operated upon; in other words, the end of the tool must be almost tangential to the circumference of the object, and the angle of the cutting edge must be obtained by removing metal from the top face of the tool. These principles are applicable to all tools for metals; to the blades of drills as well as to the cutting edges of gravers, etc.

=270.= The angle of the cutting edge of the tool used in the slide rest for steel should be less than that employed for operating on brass. According to Holtzapffel, it may vary in the former case from 60° to 80° and, in the latter case, 70° to 90°, according as the tool is required for rough turning or finishing. 60° and 80° may, however, be taken as convenient angles in the cases respectively. Simple methods of ensuring that the cutting edge has any required angle are described in article 396.

The velocity with which the lathe revolves should also be less when turning steel, and care must be taken that both the tool and object are constantly moistened with oil.

It is sometimes desirable to arrange a small dropping-can for the purpose of keeping up the supply; this may be easily done by placing a can containing the fluid above the level of the work and allowing a piece of lamp-wick, previously moistened, to hang from it so as to almost touch the work: a continuous series of drops will fall, owing to the influence of capillarity.

[Illustration: _Fig. 93._]

=271.= When roughing out work it is best that the cutter first travel perpendicular to the object, from _a_ towards _b_, Fig. 93, and then in the direction of the arrow. The corner _a_ should only be used for finishing an internal angle or for roughing it out, and, in this latter case, the cutter must advance along _a b_ and be withdrawn from the metal in the direction of the arrow. The small face at the end, _a c_, should be narrow.

[Illustration: _Fig. 94._]

=272.= =Forms of slide-rest cutters.= The usual forms of cutters for use in the slide-rest are shown in Figs. 94 and 95. A and A′ are respectively the plan and side view of the most common form. Two inclined planes _i n_ and _d c_ are formed on the left-hand and under sides. The point on which they terminate is cut off square, a cutting edge, which is more or less acute according to the metal to be operated upon, being obtained by a third incline _c n_. The width of the square cutting edge, indicated at _n_ in figure A, varies according to the metal to be operated upon, as well as this incline _c n_. It is advisable to be provided with at least half-a-dozen cutters of this form, with edges of varying width and inclination, and even this number is often found insufficient; cutters for steel should never be used in turning brass.

[Illustration: _Fig. 95._]

A cutter may be sharpened in the usual manner for ordinary work; but if it is desired to produce very smooth sinks, etc., one that has been carefully polished must be used for the final cut.

The blade should cut with both its edges; the straight edge will serve to form right-angled corners of sinks, while the other edge will form bevels. It is hardly necessary to add that, when a square corner formed by the first of these edges requires to be beveled by the second, the lathe must rotate in the opposite direction and the cutter be passed over to the opposite side of the center.

=273.= C, in the same figure, is a rounded cutter for making circular grooves. F, Fig. 95, is for cutting the groove that receives a barrel-cover. J and V are for forming the “tallow-drop” shoulders of pivot-holes, etc.

It will doubtless be observed that these cutters would form nipples that are dome-shaped and relatively somewhat high, and, for small pivot-holes, the blade would require to be narrower and of a shape that corresponds with the nipple it is desired to produce. L is for rounding off angles. S is a convenient shape for smoothing the bottom of a barrel without damage to the hook. T has a square point; it is used narrow for cutting, for example, the passage under the escape-wheel cock in a cylinder watch, and, when made wider, will serve to cut the settings for jewels. In the latter case it may either be square at the end or a little rounded at the corners.

In addition to the use indicated above, V can be employed for raising the edge of a jewel setting.

=274.= =Sharpening slide-rest tools.= A flat surface turned in the lathe will never be even unless the cutting face _n_ in A Fig. 94, is smooth, and indeed polished, and its edge parallel to the face-plate. Some care is therefore necessary in sharpening this face. The requisite parallelism can be secured by the following method.

=275.= Sharpen the tool while it is held in the tool represented in Fig. 96.

[Illustration: _Fig. 96._]

On a thick brass plate _l_ and parallel to its plane at one extremity _b_, a plate _p_ is pivoted. The inclination of _p_ to _l_ can be varied and it is fixed in any required position by the curved arc passing under the clamping screw _j_.

A small bar _c_ is fixed to _l_ with its edge set accurately at right angles to the line at _b′_ in which the two planes intersect. An examination of the figure will suffice to indicate the manner in which such a tool is used. Having set _p_ so that it makes with _l_ the angle to be given to the cutting face, the cutter _b_ is held against the bar _c_, where it may be fixed with a screw _v_, or in any convenient manner, taking care to leave the portion of the cutter that is to be removed projecting beyond the face of _p_ as shown at _b′_. Now pass a piece of smooth oilstone or disc of steel charged with oilstone dust over the face of _p_ until the projecting portion is removed; if a polished face is required, this must be succeeded by a bronze or ground glass disc charged with rouge. If the plate _p_ is of sufficient dimensions, it will not be distorted, even though only made of hammered brass; but it would of course be better made of steel, hardened if possible.

=276.= If the watchmaker will make a rectangular holder to fit in his tool post, with a square groove planed in its upper side that will fit some particular size of tool steel, say one-fourth or three-sixteenths of an inch, he can then buy bar steel of that size and make his cutters by simply cutting off a piece from the bar and grinding one end to the desired shapes and angles, thus saving a vast amount of time and labor in the preparation of his tools, facilitating their rapid interchange in the tool post, when working, and securing the greatest possible rigidity of the tool, as the cutting edge projects from the holder only far enough to allow the holder to clear the work.

GRAVERS AND OTHER HAND-TURNING TOOLS.

=277.= =Hooked gravers.= It is needless to do more than mention the gravers that some watchmakers are in the habit of making of worn-out files, of various forms to suit their special requirements; but we would remind learners that care is essential in fixing the position of the rest and the inclination that has to be given to the tool so as to obtain a smooth surface, and at the same time a rapid removal of metal.

The most usual forms of the hooked graver are shown in Fig. 97. A will serve to hollow out a plate, barrel, etc.; B for turning the bottom of a barrel without touching the hook; C for forming a barrel-cover groove after it has been roughed out with an ordinary graver. The bottom of a barrel can also be turned with a graver of the form D held on the =T=-rest at right angles to the bottom, and a slide-rest cutter can be made of this form with advantage.

[Illustration: _Fig. 97._]

Some workmen incline the end cutting face of A slightly backwards from the perpendicular to _d d_, fearing lest, in sharpening, it should accidentally be made to incline in the other direction, and so make it difficult to form internal square corners.

=278.= =Gravers for turning square shoulders, etc.= Very few watchmakers are able to finish off a square shoulder by using a graver with the usual point; as a rule, when they are smoothing the surface of the pivot they allow the point to cut a ring in the shoulder, and if, instead of being sharp, the point is dull, a rough groove is the result.

To avoid such a fault it is a common practice to employ gravers with very short faces, but their inconvenience is evident. It is much better to retain the long lozenge-shaped face, but with the point modified, as indicated by B or C, Fig. 98.

The ordinary point, shown at A, can be used for cutting the back slope of a shoulder, B for forming the square-shouldered pivot, and C for beveled shoulders. The inclination of the face _e d_ of B may vary, the angle _e_ being more or less acute, according as more or less use is required to be made of the point. This form of graver has the double advantage that a pivot can be turned and smoothed at one operation, very little polishing being needed. Moreover, the point is less fragile, and such a graver combines the advantages of those with pointed and square ends.

[Illustration: _Fig. 98._]

The length of this small face depends on the work required of it, thus for making a cylinder pivot it may be about a third the length of the pivot; this is found convenient for ensuring that the pivot shall be of uniform diameter. The direction to be given to the face is indicated by the dotted line _e d_, and a lozenge-shaped graver is preferable to one of square section for this purpose. This direction _e d_ is very important, and frequent trials should be made so as to ensure its being always produced. The form C for beveling off a shoulder does not call for explanation.

Although of less importance than when turning with the slide-rest, the cutting angle of the graver should correspond with the nature of the metal operated on. In reference to this question see article =270=.

=279.= =Spherical turning tool.= A very simple and convenient tool for forming a sphere of metal may be made by taking a hardened steel tube whose internal diameter is less than that of the sphere to be produced. This is ground square and flat at one end, and sharpened by rubbing this flat end on an oilstone. The tool is moved about over the surface of the ball, previously roughed out, and a perfect sphere will soon be obtained, the metal being removed by the internal edge of the tube. If a steel tube is not accessible it will be enough to drill a hole in the end of a softened worn-out file, subsequently hardening it.

DRILLS.

[Illustration: _Fig. 99._]

=280.= The forms ordinarily adopted for the blades of drills are shows at A and C, Fig. 99. The form C is best suited for perforating brass and other metals having a similar degree of hardness. The blade must not be too thick, as, if it were, there would not be a sufficient cutting edge. As the hardness of the metal operated on is greater, the thickness of the blade must proportionately increase, or what amounts to the same, the two slopes that give the cutting edges must have a less degree of inclination. If this condition of sufficient thickness be satisfied by a drill of the form C, it will perforate steel very well, but its point will rapidly wear. When operating on this metal, therefore, the form A is preferable, especially when the steel is at all hard. Such a drill with the corners rounded off and sharpened will last for a long time, if the cutting angles are not too acute. If the metal is not hard, more rapid progress may be made by adopting a blade less flattened than A, that is to say, something intermediate between A and C.

A drill may be asserted to be good if it satisfies the following conditions: the point must be in the middle of the blade; it must be made of good steel that is carefully hardened, without being heated beyond the proper temperature; lastly, it must be quite true—in other words, in rotating it must run with sufficient truth throughout its entire length, so that it withstands the end pressure required to cause it to bite, and does not bend.

=281.= It must not be forgotten that: (1) if a drill is driven too rapidly it will heat, and thus become softened as though too much tempered; it is with a view to prevent this that, when operating upon iron or steel, many workmen now and then dip the drill into a cold liquid (turpentine is good for this purpose), dry it, and recommence drilling, the hole being liberally supplied with oil; (2) when the blade is left too hard, the cutting edge too acute, or if a feather edge has been left by the oilstone, small hard particles that are detached from the drill will embed themselves in the hole, and this will be especially the case if it is worked too rapidly or with jerks; such particles render the operation of drilling very slow and difficult.

=282.= =To drill steel of a blue temper.= At first not much difficulty will be experienced; but when the drill reaches a certain depth and the metal seems to oppose a gradually increasing resistance, the operation must at once be stopped. If the blade of the drill be now examined with a glass, it will be easy to see which points have ceased to cut, producing instead a series of bright rings at the bottom of the hole that are very difficult to remove. Exchange the drill for one of a different form or, without reducing its width, change the form of the blade; if it was arrow-headed for example, make it a semicircle, or semi-oval, or chisel-shaped with sloping edges. All that is essential is that the form be so changed that the bright portions of the surface shall be gradually removed, and that no attempt be made to act on the whole bright surface at once. Until this hard portion is removed, the blade will require frequent sharpening.

Some authorities recommend that the hole be moistened from time to time with dilute nitric acid, which is then washed off, and renewed when a shiny surface is produced. Oil can with advantage be replaced by turpentine as a lubricant for the drill blade.

The formation of hard shining surfaces is attributed to three causes: (1) to the cutting edge being rounded, rolling as it were and hardening the surface of the metal against which it continues to move; (2) to the drill being made of bad steel or imperfectly hardened, so that small

## particles break off and are embedded in the metal operated upon; and

(3) to a deficiency in the supply of oil, or an excessive velocity of rotation of the drill.

These difficulties may usually be avoided by observing the following precautions:

[Illustration: _Fig. 100._]

=283.= _Blade of the drill._ This should be neither as thin nor as acute as is used for drilling brass. Its angle should never be less than 100° and the incline should be at about 45°. The forms generally employed are shown in Fig. 100, at A, B and C. At first the form A is used, and, as the operation progresses, it is modified with an oilstone slip.

=284.= _Drilling slowly with considerable pressure._ If the drill rotates too rapidly or there is not sufficient oil, the surfaces of contact will be heated and shining rings will form. It is well to practice slightly, varying the speed of the wheel, in accordance with the pressure applied; the speed should be more decided when the pressure is, for the instant comparatively great. With continuous rotation, considerable pressure should be applied with moderate velocity. Constantly remove the drill to sharpen, clean the hole and have an abundant supply of oil. Whatever liquid is most effective in maintaining the drill cool will probably be the best; turpentine is better than oil, since it has the additional advantage of increasing the “bite” of the drill.

=285.= _The part against which the drill acts should be very rigid._ For example, if a hole is being made for a pivot in a cylinder plug which is not provided with a shellac backing, and is, therefore, flexible, the operation will be more tedious than when the cylinder is filled with shellac. The firmness is usually greater when the object is centered about the point to which the drill is applied.

=286.= _Making the drill._ The very best steel should be used, and the precautions indicated in article =87= should be taken in the hardening. If the steel is burnt in this process, no satisfactory results are to be expected of it. To avoid such a danger it is often advisable to leave the blade nearly round and thicker than is required, finishing with a piece of oilstone. Although somewhat more tedious, this method has the advantage of ensuring that, after hardening, all the metal that is most liable to have been burnt is removed.

The drill must be short, the blade being thick and not much reduced at the shoulder, in order to stand pressure when in use. A drill that has been several times hardened is rarely good.

=287.= =Finished drills.= We would here draw the attention of watchmakers to some beautifully made drills that have been introduced and are known in the trade as “finished” drills, in contra-distinction to the well known pivot drills that are always sold in the rough. They are of two forms, corresponding to A and C, Fig. 99, for steel and brass respectively; they are made of the best steel, carefully hardened and tempered to the requisite degree; and a principal recommendation consists in the fact that, while being moderate in price, they are of definite graduated sizes, extending from 0.1 mm. to 2.5 mm. (0.004 to 0.1 inch), a range which comprises 37 distinct sizes.

=288.= =Semi-cylindrical drills.= These drills give excellent results when driven by a wheel, and, although they have been long in use by engineers, they are hardly known to watchmakers.

[Illustration: _Fig. 101._]

The simplest form is a cylindrical rod rounded at its end and then filed down to a trifle less than half its thickness, as seen at _b d_ and _l i_, Fig. 101.

The length of the point is greater or less according to the nature of the metal to be operated upon, but under no circumstances must the point itself be sharp. With the form shown at _b d_, some of the rod that is left cylindrical must be partially filed away; a better shape is indicated by the dotted lines, all the metal being removed that is outside the line _i l_. With such a drill the hole is smoothed immediately after it is made by one or the other cutting edge of the portion _i l_. It should be sharpened on the round, not on the flat surface (or at any rate very slightly), because the thickness would be rapidly reduced and the blade made smaller. When such a drill does not turn true the back of the blade can be reduced, starting from the cutting edge, it being observed that, with the continuous motion of the wheel, only one edge acts. After a few trials it will be found easy to use this form of drill.

It possesses this very great advantage: when fixed in a drill-chuck, it can be turned exactly round, of the required diameter and finished; so that, whenever replaced in the chuck, one can be certain beforehand that the hole drilled will be of a definite diameter.

[Illustration: _Fig. 102._]

=289.= Fig. 102, shows, at C and D, another form of semi-cylindrical drill; the first, C, is a front and the second a side view. The angle _a_ is formed by a sloping semicircle and the stem of the drill is of less diameter than the head, as indicated by the shoulder _j_. The angle _t s r_ and the one between the face D and the plane _b a_ must not be too acute.

This drill works evenly, but two conditions must be satisfied; it must be maintained perfectly true by the chuck, and, in commencing, both sides of the blade must engage against the sides of a conical opening that forms the beginning of a hole which has to be enlarged.

[Illustration: _Fig. 103._]

=290.= At F and N M, Fig. 103, are seen front and side views of another form of drill. While acting in a similar manner to the others described above, it differs from them in that the blade also cuts with its two sides; the edges, _p_, _i_, _i_, _o_, are sloped off backwards to form cutting angles. The shape is indicated to the right of M, this portion being the exact inverse of the side N.

As with the drills previously considered, a few trials must be made to decide upon the best slopes for the cutting angles, etc., according to the metal operated upon. They may be retained as left by the lathe, or very slightly inclined, on the faces _p_ and _i_. All these forms of drills require to be mounted so as to run very true. The point _o_ must be accurately central. A hole that has been already drilled small can be rapidly enlarged by such a drill as this last, the pin _o_, having the same diameter as the one originally drilled.

[Illustration: _Fig. 104._]

=291.= =The Twist Drill.= The Morse twist drill, shown in Fig. 104, is rapidly coming into favor with watchmakers for the heavier classes of work, and is very desirable when drilling deeply, as this form of drill heats slowly and the particles are carried to the surface of the work. A large range of sizes in these drills are now carried in stock by the material dealers.

LATHE ATTACHMENTS.

=292.= =Tailstocks.= Besides the regular tailstock which accompanies the American lathe there are several other varieties made for use on special kinds of work. Fig. 105 illustrates the half open tailstock which is cut away so that the spindles can be laid in, instead of being passed through the holes. The fixture will be found exceedingly convenient when several spindles are to be used for drilling, counterboring and chamfering. Fig. 106 illustrates the screw tailstock, an attachment which is very convenient for all kinds of heavy drilling, the spindle being moved by a screw with hand-wheel attached. Fig. 107 illustrates the traverse spindle tailstock, which will be found very convenient for straight drilling and especially where the watchmaker has considerable drilling to do.

[Illustration: _Fig. 105._]

[Illustration: _Fig. 106._]

[Illustration: _Fig. 107._]

[Illustration: _Fig. 108._]

=293.= =Jeweling Caliper Rest.= Although this tool was invented and manufactured for the purpose of cutting jewel settings it may be used to great advantage in countersinking for screw heads, opening wheels for pinions or bushings, etc. The sliding jaws of the calipers should be so adjusted that when the swinging part is brought back snugly against them, the front cutting edge of the cutter in the sliding spindle will exactly line with the center of the lathe spindle. Then if the calipers are at the right height, when a jewel or jewel setting is placed in the jaws of the caliper it will move the edge of the cutter outward from the lathe center just half the diameter of the jewel then in the caliper and the cutting made at that distance from the center will exactly coincide with the size of the jewel to be set. If however, when set and worked as above, it is found that the hole cut is too large for the jewel, it will indicate that the calipers are too low down and should be raised, provision for which is made in the construction of the tool. Upon the other hand, if the cutting is found too small to fit, it will indicate the calipers should be lowered. The final cutting for the jewel seat should be made by running the center straight inward from the face of the plate; the adjustable stop screw on the back end of the sliding spindle, serving to gauge the depth of the cutting.

[Illustration: _Fig. 109._]

[Illustration: _Fig. 110._]

[Illustration: _Fig. 111._]

[Illustration: _Fig. 112._]

=294.= =Pivot Polishers.= The pivot polisher is used for grinding and polishing conical and straight pivots and shoulders. It is also used for drilling, polishing or snailing steel wheels, milling out odd places in plate or bridge, where only a part of a circle is to be removed, etc. In the style shown in Fig. 109, the American Watch Tool Co.’s polisher, and Fig. 110, the Moseley pattern, the circular base is graduated to degrees and the fixture can be set at any angle. The spindle has a taper hole for drill chucks, which makes the fixture very useful for drilling either in the center or eccentric and by using the graduations on the pulley of the headstock an accurately spaced circle of holes may be drilled. Fig. 111 illustrates the polisher made by the Faneuil Watch Tool Company, and is intended to be mounted on the slide rest. Fig. 112 illustrates the Johanson pivot polisher and in general principle is like the others. This style is made both for use on the slide rest and also for the hand rest. When used in the latter, a stud, shown in Fig. 113, is screwed into the base plate and supports the tool in the hand rest, so as to be readily adjustable in any direction. When used in the slide rest, this stud is removed and the plate clamped between two hollow cylindrical supports by a stud which is slipped into the groove of the slide rest and fasted by a nut at the top, the whole forming a turret-like mount of great strength and upon which the machine can be readily swiveled in any direction. In general, polishers are used as follows: After the pivot is turned to proper shape, put on your polisher, with the lap back of the pivot, usually the cast iron lap first. A square-cornered lap for square shoulders and a round-cornered lap for conical pivots. The laps for conical pivots can be readily cornered with a fine file, and cross-ground with fine oilstone to remove any lines made by graver or files. Lines on the end can be removed the same way, or by means of the fingers often rubbing them on a piece of ground glass which has on it a paste of oilstone powder and oil, well mixed. Oilstone powder and oil used on the lap, or No. 1 crocus will rough out the work well. When roughed out to your liking, wipe off the oilstone powder or crocus and with a little oil touch the pivot gently; repeat the second time. Then change lap for one of boxwood or brass and use crocus No. 4, very fine, and ground down to a paste. Proceed as with the first lap, being careful at all times to keep the lap properly oiled and not pressed too hard against the work, particularly in the last operation. Be sparing of your grinding and polishing material as a little will accomplish as much work as a large quantity and do it better. Bring the lap up carefully against the work until spread all the way around, then proceed, bearing in mind that grinding is not polishing, and that to polish nicely the work and lap must be very nearly the same shape. Fig. 114 illustrates the Hardinge pivot polisher, which is a hand polisher and much more simple in construction and use than those mentioned above. It is attached to the lathe bed the same as the T or hand rest. Polishing and grinding slips are furnished with this attachment, as with the others.

[Illustration: _Fig. 113._]

[Illustration: _Fig. 114._]

=295.= =Centering Attachments or Back Rests.= These attachments are very useful in rapidly bringing work to an accurate center, when pivoting, staffing, etc., and particularly where a large number of pieces have to be centered successively. Fig. 115 illustrates the Potter patent self-centering lathe attachment which is made to fit any pattern of American lathe.

[Illustration: _Fig. 115._]

It consists principally of the slide bed pieces _R_ and _D_, the upright plate _A_ and the reversible anti-friction sliding jaws _O U V X_. The upright plate _A_ is attached to the slide _D_ in such a way that it may be readily raised or lowered, or adjusted in any other direction at pleasure; and may be set with either side facing the lathe-head. The sliding jaws are made of phosphor bronze anti-friction metal and four sets, of three in a set, are furnished with each attachment, as shown at _O_, _U_, _V_, _X_, the forms differing so they may be adapted to the various kinds of watch work, and they are operated in radial grooves in the upright plate _A_ by means of the rotating lever _L_, which moves the three jaws in and out, to and from the center, or opens and closes them in perfect unison. One set of jaws may be withdrawn and another set substituted therefor in a few moments. With each change of the jaws, however, the plate _A_ requires readjustment, but this too, may be done in a few moments, as follows: Having previously provided yourself with a bit of straight wire or a small steel rod, turned to run perfectly true in your lathe, and having fastened this in your chuck in the lathe, loosen the nuts _C C_, so as to give freedom of movement to the plate _A_; then bring the attachment to proper position on the lathe bed and fasten it there, after which move the sliding jaws inward until they bind tightly on the piece of straight wire held in the chuck and in this position again tighten the nuts _C_ _C_. Once adjusted to accurate center in this way, no further adjustment, whatever the size of the work to be operated upon, is required, until you make another change of jaws.

In use, the end of the work to be operated upon is placed in an accurate split chuck in the lathe, and the chuck tightened on it, just sufficiently to hold it in place and to rotate it, the other end being supported in the central bearing, formed by the sliding jaws. In this position the jaws may be opened or closed as often as desired, and each time they will bring the work to accurate center.

A similar attachment to the one above described is extensively used by machinists and is known as the back rest. In principle it is very similar, but is more simple in construction, and ambitious workmen can make them without difficulty. This attachment, which is shown in Fig. 116, differs in its mode of fastening to the lathe bed and the jaws cannot be opened and closed at one time as in the Potter attachment.

[Illustration: _Fig. 116._]

The illustration shows the rest in position on the lathe bed, looking from the right-hand end of bed; _m_ shows the base, looking from above, in direction of arrow _k_; _d_ shows bolt for binding it to the lathe bed. It does not seem as though it needed much explanation, as it will be readily seen that the head _d_ of bolt, passes up through the longitudinal slot in the lathe bed, through the round hole in base of back rest and is slipped back into slot _m_, when about half a turn of nut _g_ binds it firmly to the bed. The washer _h_, on the end of the binding screw, is riveted or soldered in place and should be close enough to nut _g_ to allow only about half a turn to loosen the bolt, as that is sufficient, and more space would occasion a loss of time in running the nut back and forth to bind or loosen the rest. It will be seen that when the nut _g_ is slackened, it binds against the washer _h_, and it will stay there, and be just where you want it when you are ready to use it again. The jaws are of hard brass; about three sets, with points of different widths, will cover a large range of work. Those shown in Fig. 116 are suitable for such work as pivoting small French clock pinions, etc. It will be observed that the jaws are so made that they may be changed by slightly loosening the screws. The screw heads should have thin steel washers under them.

[Illustration: _Fig. 117._]

[Illustration: _Fig. 118._]

=296.= =Universal Head.= The universal head has entirely superseded the clumsy universal mandrel in this country. The example shown in Fig. 117 is more accurate, less clumsy and complicated and will perform all the work that can be performed on the universal mandrel. The face-plate is 3½ inches in diameter, but by the use of the two crescent-shaped slots it will hold anything in size and shape of watch work. The pump center is operated from the back by the rubber knob and can be used either with or without a spring. The jaws, which will pass the center, are held in position on face of plate by springs and are fastened from the back. Peep holes are provided in these heads in order that the workman may examine the back of the work at all times. In the Moseley head, shown in Fig. 117, these holes are of taper form. Fig. 118 shows a universal face-plate to be used in a chuck in the lathe. It is smaller and less expensive than the universal head and answers very well for some work, especially that of the lighter kind, but cannot be recommended as highly as the universal head, as it is not so accurate. The pump center is used to center, from the back, any object confined in the jaws, but it sometimes becomes necessary to mount the object, by means of wax, upon a plate, and hold the plate in the jaws. In such a case the work must necessarily be centered from the front. This can be done accurately by means of a piece of pegwood, as ordinarily done on the lathe, by placing the point in the center hole and the pegwood resting on the T-rest and observing if the free end of the pegwood remains stationary.

=297.= =Traverse Spindle Grinder.= This tool will be found very useful for grinding cutters, lathe centers, pump centers, reamers, countersinks, squaring up barrel arbors after hardening, or work on any hardened steel tool. In the hands of an ingenious workman, it will be found exceedingly useful, as by its aid a great variety of work can be performed that cannot be accomplished without it. Fig. 119 is intended to be attached to the slide rest.

[Illustration: _Fig. 119._]

[Illustration: _Fig. 120._]

=298.= =Milling Fixture.= This attachment, which is shown in Fig. 120 is designed to be fitted to the slide rest and holds the wire chuck vertically under the center of the lathe, so that articles held in the chucks can be fed under mills or saws held in the saw arbor in the lathe-head.

[Illustration: _Fig. 121._]

=299.= =Wheel Cutters.= The wheel cutter is a valuable addition to the lathe. Several different styles of these attachments are made, each possessing points of merit. They are designed for cutting all kinds of wheels and pinions used in key and stem-wind watches. When the cutter spindle is vertical the belt runs directly to it from the countershaft, but when horizontal, the belt passes over idler pulleys held above the lathe. One style of wheel-cutting attachment is shown in Fig. 121, while another style is shown in Fig. 71.

[Illustration: _Fig. 122._]

=300.= =Rounding-up Attachment.= The Webster rounding up attachment, shown in Fig. 122, is a very useful adjunct to the lathe. It is attached to the top of the slide-rest. To operate, a pointed taper chuck is put in the lathe spindle. The wheel to be rounded up is put into the fixture and the wheel adjusted vertically so that the point of the lathe center will be at the center of the thickness of the wheel, after which the lower spindle of the fixture should not be moved. Now remove the wheel, also the taper chuck, and put the saw arbor, with the rounding-up center, in the lathe spindle, and adjust the longitudinal slide of the slide-rest so that the rounding-up cutter will be back of and in line with the center of the rounding-up fixture, after which the longitudinal slide of the slide-rest should not be moved. Now put the wheel and supporting collet in place, and proceed with the rounding-up.

MISCELLANEOUS SMALL TOOLS.

[Illustration: _Fig. 123._]

=301.= =Screw Head Sink Cutter.= This is usually made in the form of an arbor terminating in a cutting edge similar to the rose-cutter, but having a projecting pin from its center. This tool will be found especially useful in replacing broken end-stones. The jewel being set in brass, is held by two screws, on opposite sides, the screw heads being let in or sunk even with the surface, half of the screw head projecting over on the end-stone. The end-stones furnished by the watch companies are not sunk for these screw heads, but are round and of the proper diameter. These cutters will cut away from the jewel setting the space to be occupied by the screw head in a very few moments and in a very perfect manner. All of the watch companies do not use the same diameter of screw head in the cock and potance, consequently you will be compelled to make separate tools for the different makes of watches. With a set of five or six of these cutters you can fit any American watch. After you have completed your set, of say five or six cutters, select a small brass plate and bore five or six small holes in a row, in which the guide pins of the cutters will enter, and then cut with the tools a number of sinks, numbering these holes in the plate and also the arbors of the tools with corresponding numbers. You will then have a plate similar to Fig. 123 which can then be used as a gauge for measuring the heads of screws.

[Illustration: _Fig. 124._]

These cutters are easily made as follows: cut off a piece of wire of the required diameter, about one inch long, and place it in a chuck that fits it snugly and turn one end to a center, about 40°; now reverse the wire in the chuck and be sure it is true; select a drill that will pass through the screw hole in the cock or potance freely and proceed to drill a hole in the center of the end of the wire, about ¹⁄₁₆ of an inch deep. Remove from the lathe and with a sharp file and graver, proceed to cut a series of teeth as equal and even as possible. Use a good strong glass while working and be sure you have every tooth sharp and perfect, as upon this depends the quick and nice work you expect from the tool. When this is well done, proceed to temper fairly hard and polish up the outside to make it look workmanlike. Now select a piece of steel pivot wire, of a size that will almost fit in the hole drilled in the end of the tool and polish down to the proper size to drive in the hole tightly. Allow the wire to project about ¹⁄₁₆ of an inch, taper the point and polish. The tool is now complete and will resemble Fig. 124. Select an end-stone of a diameter to fit tightly in the cock or potance, as maybe required; set the hole jewel in place and then the end-stone pressed down tightly against the hole jewel. Place your cutter in a chuck that fits it true; select a smaller medium sized drill rest and place it in the tail stock spindle. Hold the cock, or potance, with the jewels in place, against the drill rest, level, and proceeding to run the lathe at a fair speed, slowly feed the cock or potance to the cutter, the projecting pivot in the end of the cutter passing through the screw hole and acting as a guide to keep the cutter in the center of the hole. Caution must be exercised, or you will cut the recess for the screw heads too deep, as these little cutters are very deceiving and cut much faster than you would suppose. In fitting an end-stone, select one that is more than flush when the jewel hole and end-stone are in the proper position, and after sinking the screw head as described, turn off on the lathe almost flush or level. Make a small dot on one side of the end-stone as a mark or guide in replacing it. Remove the end-stone and proceed to polish the top of the setting on a plate glass polisher.

=302.= =Screw Extractors.= The Bullock Screw Extractor, shown in Fig. 125, is a simple yet very valuable tool to the watchmaker who finds he has a plate in which a screw has been broken off. To use this tool, first fasten it in your vise, then bring one end of the broken or rusted-in screw against screw center and the broken screw head against screw driver; turn the washers so as to hold the broken screw firmly in place; turn the plate gently and the broken screw will follow the screw driver point out of the plate. It may be necessary in some instances to turn the screw driver point against the broken head with a good deal of force in order to start the screw. A little benzine or kerosene applied to the screw will help to loosen it.

[Illustration: _Fig. 125._]

The ingenious workman can, with the expenditure of a little time, make an attachment for removing broken screws, somewhat similar to the above. Take two common steel watch keys having hardened and tempered pipes—size, four or five—having care that the squares in each are of the same size and of good depth. Cut off the pipes about half an inch from the end; file up one of these for about one-half its length, on three equal sides, to fit one of the large split chucks of the lathe. Drill a hole in one of the brass centers of the lathe of sufficient size and depth, into which insert the other key-pipe, and fasten with a little solder. Soften a piece of Stubbs’ wire, to work easily in the lathe, and turn down for an eighth of an inch from the end to a size a little smaller than the broken screw in the plate; finish with a conical shoulder, for greater strength, and cross-file the end with a fine slot or knife-edge file, that the tool may not slip on the end of the broken screw; cut off the wire a half inch from the end and file down to a square that will fit closely in one of the key-pipes. Make a second point like the first one and fit it to the other key-pipe; harden in oil, polish, and temper to a dark straw color. Fit the brass center into the tail stock. To use, put the tools in place in the lathe, place the broken end of the screw against the end of the point in the lathe-head; slide up the back center and fasten the point firmly against the other end of the screw, that it may not slip or turn; revolve the plate slowly, and the broken screw, being held fast between the two points will be quickly removed. To remove a broken pillar screw, place the broken screw against the point in the lathe-head, holding the plate firmly with the right-hand, the pillar on a line with the lathe center; turn the lathe-head slowly backward with the left-hand, and the screw will be removed. Should the tool slip on the broken screw, and fail to draw it out, drill a hole in the lower or dial side of pillar, down to the screw point (if the size of the pillar will admit of it), and with the second point in the back center, remove the screw in the same manner as in the first process. Five or six sizes of these points will be found sufficient for the majority of these breakages that may occur.

It sometimes happens that a screw gets broken off in a watch plate in such a manner that it is impossible to remove it with tools without marring the plate. In such an event proceed as follows: Put enough rain water in a glass tumbler to thoroughly cover the plate and add sulphuric acid, until the water tastes a little sharp. Place the plate in the solution and allow it to remain a few hours, when the screw will partially dissolve and drop out. Remove from the solution, wash thoroughly in clean water, then in alcohol and dry in saw dust. The solution will not injure the brass plate or gilding in the slightest, but care must be taken to remove all other screws or cemented jewels, previous to immersion.

[Illustration: _Fig. 126._]

=303.= =Roller Remover.= There are numerous designs in the way of roller removers upon the market, some of them good but many of them weak and liable to bend where the roller is very tight on the staff. All points being considered, the Hardinge remover, shown in Fig. 126, is perhaps the strongest and best on the market and is built on true mechanical principles.

The nose in the center and top of the illustration is drilled up so as to receive a balance pivot without bearing on its point, and can be moved towards or from the two bent prongs by means of the thumb nut at the bottom of the tool. The prongs can be spread apart or drawn together, and are secured in place by means of the binding screws at the sides. In using the remover the feet of the two prongs are brought under the roller and secured by the binding screws. The nose is now advanced against the shoulder of the bottom pivot and the staff can be driven out without damage to either roller or staff.

[Illustration: _Fig. 127._]

=304.= =Balance Protectors.= These are of two kinds and for entirely different operations. The Arrick protector, shown in Fig. 127, is used for protecting balances while working upon the pivots while in the lathe. No matter how careful a person may be, accidents will happen, and the least accident to a compensation balance gives the workman considerable trouble. The least slip of the graver, polisher or hand rest and great damage is the result. The staff is passed through the hole in the protector, and held in a wire chuck, and the protector is secured to the arms of the balance by two screws. The Bullock protector, shown in Fig. 128, is designed to protect the balance and other wheels from heat while drawing the temper from staff or pinion for the purpose of pivoting.

[Illustration: _Fig. 128._]

[Illustration: _Fig. 129._]

=305.= =Beat Block.= This simple device obviates the necessity of marking the balance to see that it is in beat. Before taking off the hair spring lay it on the block, shown in Fig. 129, turn the balance so the roller pin hits on the side the arrow points, then turn the table so that the line comes under the stud. In replacing the balance put the stud over the line and it will then beat the same as before. By using this tool you also avoid getting the balance out of true.

=306.= =Female Centers.= Centers are of two kinds,, male and female. The ordinary centers that accompany the lathe, which are male centers, are familiar to all watchmakers. Female centers, however, are not so well known among watchmakers, and they can be used to great advantage in many operations where other and less simple attachments and means are usually resorted to. You should have at least six pairs of female centers, the largest being one-fourth of an inch in diameter, which will accommodate as large a piece as you will wish to handle on your watch lathe, viz: winding arbors for clocks. These female centers are made from steel tapers, the same as male centers are made, but instead of turning the end to a sharp point they are countersunk, Fig. 130. First place the taper in a chuck and turn off the outside and end true; drill a small hole in the center of the taper, while the lathe is running, and deep enough so the countersink will not reach the bottom of the hole, or one-eighth of an inch deeper than the countersink. Harden the end only, and after tempering polish off the bluing. After you have made all the sizes you require, test all of them in your lathe to make sure they did not get out of true in tempering.

[Illustration: _Fig. 130._]

These female centers are very useful for holding or suspending any article in the lathe that is too large to be held in the split chucks. Pivots of clocks can be turned and polished very quickly and accurately in these centers.

Almost any kind of large work can be done on a medium sized watchmaker’s lathe by fitting to it a face plate one and three-fourths inches in diameter, with four slots, and fitted to a chuck with a standard taper hole to receive both male and female centers interchangeably. With two styles of dogs, almost any kind of large clock work can be readily handled.

These centers prove very useful for many odd jobs. As an example: It is a very common occurrence to hear an American clock beat irregularly, caused by the escape wheel being out of round. Select a pair of female centers that will admit the ends of the pivots of the escape wheel snugly; place one center in the taper chuck and the other in the tail stock spindle, and suspend the escape pinion in these centers; fasten on a dog, run the lathe at a high speed and hold a fine sharp file so it will touch the teeth of the ’scape wheel slightly, and in a moment the wheel will be perfectly round, after which sharpen up the teeth that are too thick.

[Illustration: _Fig. 131._]

=307.= =Drill Rest.= In using the lathe for drilling, a great saving in both time and drills can be effected by using a drill rest similar to that shown in Fig. 131. It is well to have a half dozen different sizes, starting at ¼ inch and increasing by ⅛ inch, for various classes of work. These rests are not kept by material dealers, but can be made by the watchmaker. Saw from a piece of rolled sheet brass, say 1-16 inch thick, the circles required, leaving metal enough to finish nicely. Place a steel taper plug in the taper chuck of your lathe and turn down a recess, leaving a shoulder on the taper. Drill a hole through the brass plate to fit the steel taper tightly. Place the end of the taper on a lead block and proceed to rivet the brass plate, on the taper, making sure that it is true replace the taper in the lathe chuck and proceed to turn the face and edge of the brass plate perfectly true and to the proper size. Those who have tried to drill a straight hole through an object by holding it in the fingers know just how difficult it is to do, but by placing one of these drill rests in the spindle of the tail stock, placing the article to be drilled against it and bringing it up against the drill, you can drill the hole perfectly upright and avoid all danger of breaking the drill.

[Illustration: _Fig. 132._]

=308.= =Filing Fixture or Rest.= These rests will be found very convenient in squaring winding arbors, center squares, etc. There are several makes of these tools, but they are all built upon the same principle, that of two hardened steel rollers on which the file rests, and Fig. 132 is a fair example. One pattern is made to fit in the hand rest after the =T= is removed, while the other is attached to the bed of the lathe in the same manner as the slide rest. The piece to be squared is held in the split or spring chuck in the lathe, and the index on the pulley is used to divide the square correctly. Any article can be filed to a perfect square, hexagon or octagon as may be desired. The arm carrying the rollers can be raised or lowered as required for adjustment to work of various sizes.

=309.= =Filing Block.= A contrivance made to take the place of the filing rest, which was made of box wood or bone. Ide’s filing fixture, shown in Fig. 133, consists of a cylinder of hardened steel, riveted upon a staff which in turn enters a split socket. The surface of the steel cylinder is grooved with various sizes of grooves for the different sizes of wire, or to suit any work.

[Illustration: _Fig. 133._]

[Illustration: _Fig. 134._]

Fig. 134 illustrates Melotte’s revolving bench block, which combines both anvil and filing block. No. 1 is a steel anvil which may be instantly revolved and stopped on quarters. No. 2 is a rubber block, held by friction on its arm, and can readily be turned to any position. This rubber, being slightly elastic, makes a very suitable filing bed for small articles of any material and may be used without risk of scratching or defacing polished surfaces. No. 3 is a wooden block, held on to its arm by a spring friction device, which also allows it to be turned around to any desired position. The three-armed hub is revolved by pulling out slightly and is automatically held perfectly firm and solid in any of the three positions.

[Illustration: _Fig. 135._]

=310.= =Micrometer Caliper.= Fig. 135 is a full size cut of the Brown & Sharp Mfg. Co.’s micrometer caliper. It measures from one-thousandth of an inch to one-half inch. It is graduated to read to thousandths of an inch, but one-half and one-quarter thousandths are readily estimated. This instrument is also graduated to the hundredths of a millimeter, but when so graduated the table of decimal equivalents is omitted. They are also made to read to ten thousandths of an inch. The edges of the measuring surfaces are not beveled, but are left square, as it is more convenient for measuring certain classes of work. It will gauge under a shoulder or measure a small projection on a plain surface. Watchmakers will especially appreciate micrometers of this form. This tool will be found very useful for gauging mainsprings, pinions, etc. In the caliper, shown by cut, the gauge or measuring screw is cut on the concealed part of the spindle C, and moves in the thread tapped in the hub A; the hollow sleeve, or thimble D is attached to the spindle C and covers and protects the gauge screw. By turning the thimble, the screw is drawn back and the caliper opened.

The pitch of the screw is 40 to the inch. The graduation of the hub A, in a line parallel to the axis of the screw, is 40 to the inch, and is figured 0, 1, 2, etc., every fourth division. As the graduation conforms to the pitch of the screw, each division equals the longitudinal distance traversed by the screw in one complete rotation, and shows that the caliper has been opened 1-40th or .025 of an inch. The beveled edge of the thimble D is graduated into 25 equal parts, and figured every fifth division 0, 5, 10, 15, 20. Each division when passing the line of graduation on hub A, indicates that the screw has made 1-25th of a turn, and the opening of the caliper increased 1-25th of 1-40th, or a thousandth of an inch.

Hence, to read the caliper, multiply the number of divisions visible on the scale of the hub by 25, and add the number of divisions on the scale of the thimble, from zero to the line coincident with the line of graduation on hub. For example: As the caliper is set in the cut, there are three whole divisions visible on the hub. Multiply this number by 25, and add the number of divisions registered on the scale of the thimble, which is 0 in this case, the result is seventy-five thousandths of an inch. (3 × 25 = 75 0 = 75). These calculations are readily made mentally.

Differences between Wire Gauges in Decimal Parts of an Inch.

Key: A - No. of Wire Gauge. B - American or Brown & Sharpe. C - Birmingham or Stubs’. D - Washburn & Moen Manufacturing Co., Worcester, Mass. E - Trenton Iron Co., Trenton, N.J. F - New British. G - Old English from Brass Mfrs. List. H - No. of Wire.

================================================================== A | B | C | D | E | F | G | H -------+---------+------+-------+--------+-------+--------+------- 000000 | ---- | ---- | .46 | ---- | ---- | ---- | 000000 00000 | ---- | ---- | .43 | .45 | ---- | ---- | 00000 0000 | .46 | .454 | .393 | .4 | .4 | ---- | 0000 000 | .40964 | .425 | .362 | .36 | .372 | ---- | 000 00 | .3648 | .38 | .331 | .33 | .348 | ---- | 00 0 | .32495 | .34 | .307 | .305 | .324 | ---- | 0 1 | .2893 | .3 | .283 | .285 | .3 | ---- | 1 2 | .25763 | .284 | .263 | .265 | .276 | ---- | 2 3 | .22942 | .259 | .244 | .245 | .252 | ---- | 3 4 | .20431 | .238 | .225 | .225 | .232 | ---- | 4 5 | .18194 | .22 | .207 | .205 | .212 | ---- | 5 6 | .16202 | .203 | .192 | .19 | .192 | ---- | 6 7 | .14428 | .18 | .177 | .175 | .176 | ---- | 7 8 | .12849 | .165 | .162 | .16 | .16 | ---- | 8 9 | .11443 | .148 | .148 | .145 | .144 | ---- | 9 10 | .10189 | .134 | .135 | .13 | .128 | ---- | 10 11 | .090742 | .12 | .12 | .1175 | .116 | ---- | 11 12 | .080808 | .109 | .105 | .105 | .104 | ---- | 12 13 | .071961 | .095 | .092 | .0925 | .092 | ---- | 13 14 | .064084 | .083 | .08 | .08 | .08 | .083 | 14 15 | .057068 | .072 | .072 | .07 | .072 | .072 | 15 16 | .05082 | .065 | .063 | .061 | .064 | .065 | 16 17 | .045257 | .058 | .054 | .0525 | .056 | .058 | 17 18 | .040803 | .049 | .047 | .045 | .048 | .049 | 18 19 | .03539 | .042 | .041 | .039 | .04 | .04 | 19 20 | .031961 | .035 | .035 | .034 | .036 | .035 | 20 21 | .028462 | .032 | .032 | .03 | .032 | .0315 | 21 22 | .025347 | .028 | .028 | .27 | .028 | .0295 | 22 23 | .022571 | .025 | .025 | .024 | .024 | .027 | 23 24 | .0201 | .022 | .023 | .0215 | .022 | .025 | 24 25 | .0179 | .02 | .02 | .019 | .02 | .023 | 25 26 | .01594 | .018 | .018 | .018 | .018 | .0205 | 26 27 | .014195 | .016 | .017 | .017 | .0164 | .01875 | 27 28 | .012641 | .014 | .016 | .016 | .0148 | .0165 | 28 29 | .011257 | .013 | .015 | .015 | .0136 | .0155 | 29 30 | .010025 | .012 | .014 | .014 | .0124 | .01375 | 30 31 | .008928 | .01 | .0135 | .013 | .0116 | .01225 | 31 32 | .00795 | .009 | .013 | .012 | .0108 | .01125 | 32 33 | .00708 | .008 | .011 | .011 | .01 | .01025 | 33 34 | .006304 | .007 | .01 | .01 | .0092 | .0095 | 34 35 | .005614 | .005 | .0095 | .009 | .0084 | .009 | 35 36 | .005 | .004 | .009 | .008 | .0076 | .0075 | 36 37 | .004453 | ---- | .0085 | .00725 | .0068 | .0065 | 37 38 | .003965 | ---- | .008 | .0065 | .006 | .00575 | 38 39 | .003531 | ---- | .0075 | .00575 | .0052 | .005 | 39 40 | .003144 | ---- | .007 | .005 | .0048 | .0045 | 40 -------+---------+------+-------+--------+-------+--------+-------

[Illustration: _Fig. 136._]

=311.= =Registering Gauge.= The registering gauges shown in the illustrations are two of the best examples of this class of tools. They are manufactured by A. J. Logan, Waltham, Mass., and are very accurate and nicely finished. Fig. 136 is an upright and jaw gauge, and Fig. 137 is designed as a jaw and depth gauge. They are both made to gauge one-thousandth of a centimeter or one-thousandth of an inch. Fig. 137 shows the piece of work marked A being gauged, while B represents a sliding spindle to get the depth of a hole or recess, or the thickness of any piece of work, which will be indicated on the dial.

[Illustration: _Fig. 137._]

[Illustration: _Fig. 138._]

[Illustration: _Fig. 139._]

Another form of registering gauge is shown in Fig. 138. It is an English gauge and but little used in this country. The principle of its construction, however, is good, and any ingenious watchmaker can make it. The back of the dial is recessed and arranged as in Fig. 139. One limb is fixed; the other is pivoted, and has a few rack teeth meshing into a center pinion. The pinion carries the hand, which should make a revolution in closing the calipers. The spiral spring attached to the pinion is to keep it and the hand banked in one direction for shake. The spring _s_ is to keep the jaws open. The milled headed screw and the clamp _c_ are to fix the jaws in case it is required to do so. A cover is snapped into the recess, and takes the back pivot of the pinion.

[Illustration: _Fig. 140._]

=312.= =Staff Gauge.= The tool shown in Fig. 140 is designed for measuring the height of the balance staff from the balance seat to the end of the top pivot. The illustration is enlarged to give more distinctness. _E E′_ is a piece of curved steel about ¹⁄₂₀ of an inch thick, and ¹⁄₂₅ of an inch wide. On the lower side from _E′_ to the end, the arm is filed down in width and thickness to correspond to an ordinary balance arm; _C_ is a slot in the upper arm _E_, which allows _A_, _B_, _D_, _A′_ to be moved backward and forward. _D D′_ is a round brass post drilled and tapped. The part _D′_ has a thread cut on it, and the part shown in the slot _C_ fits with easy friction. _B_ is a lock-nut, drilled and tapped to fit the thread on _D′_. It is for the purpose of clamping _D D′_ against the arm _E_. _A A′_ is a small steel screw with milled head, and is made to fit the tapped hole in _D D′_.

Mr. Beeton describes his method of using this tool as follows: Take your measurement of the distance _the balance seat is to be from the end of the top pivot_, as follows: remove the end-stone in balance-cock, and screw the cock on the top of the top plate (18-size full plate movement); then taking the plate in your left-hand, and tool (shown in Fig. 139) in your right, place _H_ in position, so that the end of the screw _A′_ rests on the jewel in the balance cock, and notice the position of the arm _E′_ which corresponds to the balance arm, between the top plate and under side of the balance-cock. If the distance between the arm _E′_ and end of screw _A′_ is too great, the arm _E′_ will be too low and touch the plate; if not enough, it will be too high and touch the regulator pins. Therefore, all that is necessary to do is to move the screw _A A′_ up or down as the case may be, sufficiently to ensure that the arm _E′_ will assume the position the _arm of the balance_ is to have. Take an 18-size balance with oversprung hairspring, the arm is at the bottom of the rim; in that case, when measuring, the screw _A′_ is adjusted so as to bring the arm _E′_ close to the plate, when _A′_ is resting on the balance jewel; if the balance is old style with undersprung hairspring, the balance arm is at top of rim, in which case _A′_ is adjusted so that the arm _E′_ is close to the balance cock; if the balance arm is in the center of the rim, as in some English and Swiss balances, the screw _A′_ is adjusted so that the arm _E′_ is midway between the plate and cock.

The reason the part _A_, _B_, _D_, _A′_ are arranged to move laterally in slot _C_ is, because all balance shoulders are not the same distance from the center, and where, in some cases, the screw _A′_ would be in a line with the center of the staff when the arm _E′_ was resting on the balance seat, in other cases it would reach past the center, of course, short of it; and, therefore, it is made adjustable to suit all cases.

[Illustration: _Fig. 141._]

=313.= =Staff or Cylinder Height Gauge.= The obvious advantage of this tool, which is shown at Fig. 141, is the automatic transfer of the measurement so that it may be readily applied to the work in hand. The tool, as the illustration shows, consists of a brass tube terminating in a cone-shaped piece. To the bottom of this cone is attached a disc through which a needle plays. Around the upper end of the tube is a collar upon which is fixed a curved steel index finger. A similar jaw, which is free to move, works in a slot in the tube. The movable jaw is tapped and is propelled by a screw that terminates in the needle point. This tool is very useful in making the necessary measurements required in putting in a staff. To use it in this work, set the pivots of the gauge through the foot hole, and upon the end-stone project the needle such a distance as you wish the shoulder to be formed above the point of the pivot. Next set the gauge in the foot hole as before, and elevate the disc to a height that shall be right for the roller, which is done by having the lever in place, the little disc showing exactly where the roller should come. Finish the staff up to that point; then take the next measurement from the end-stone to where the shoulder should be, for the balance to rest upon. This point being marked, the staff can be reversed and measurements commenced from the upper end-stone, by which to finish the upper end of the staff. Distances between the shoulders for pinions and arbors can be obtained with the same facility, a little practice being the only requisite.

=314.= =Vernier Caliper.= Fig. 142 is an illustration of the Vernier Caliper, a light, convenient and valuable instrument for obtaining correct measurements. The side represented in the illustration is graduated upon the bar to inches and fiftieths of an inch, and by the aid of a Vernier is read to the thousandths of an inch (see description below). The opposite side is graduated to inches and sixty-fourths of an inch. The outside of the jaws are of suitable form for taking inside measurements, and when the jaws are closed, measure two hundred and fifty thousandths of an inch in diameter.

[Illustration: _Fig. 142._]

These instruments can be furnished with millimeters (in the place of sixty-fourths of an inch), and provided with a Vernier to read to one-fiftieth of a millimeter.

On the bar of the instrument is a line of inches numbered 1, 2, 3, each inch being divided into tenths, and each tenth into five parts, making fifty divisions to one inch. Upon the sliding jaw is a line of divisions (called a Vernier, from the inventor’s name), of twenty parts, figured 0, 5, 10, 15, 20. These twenty divisions on the Vernier correspond to extreme length with nineteen parts, or nineteen-fiftieths on the bar, consequently each division on the Vernier is smaller than each division on the bar by one-thousandth of an inch. If the sliding jaw of the caliper is pushed up to the other, so that the line 0 on the Vernier corresponds with 0 on the bar, then the next two lines on the left will differ from each other one-thousandth of an inch, and so the difference will continue to increase one-thousandth of an inch for each division till they again correspond on the twentieth line on the Vernier. To read the distance the caliper may be open, commence by noticing how many inches, tenths and parts of tenths the zero point on the Vernier has been moved from the zero point on the bar. Then count upon the Vernier the number of divisions until one is found which coincides with one on the bar, which will be the number of thousandths to be added to the distance read off on the bar. The best way of expressing the value of the divisions on the bar is to call the tenths one hundred thousandths (.100) and the fifths of tenths, or fiftieths, twenty thousands (.020). Referring to the accompanying cut, it will be seen that the jaws are open one-tenth of an inch, which is equal to one hundred thousandths (.100). Suppose now, the sliding jaw was moved to the left, so that the first line on the Vernier would coincide with the next line on the bar, this would then make twenty thousandths (.020) more to be added to one hundred thousandths (.100), making the jaws then open one hundred and twenty thousandths (.120) of an inch. If but half the last described movement was made, the _tenth line on the Vernier_ would coincide with a line on the bar, and would then read, one hundred and ten thousandths (.110) of an inch.

[Illustration: _Fig. 143._]

=315.= =Hair Spring Stud Index.= Fig. 143 illustrates Johanson’s hair spring stud index. The engraving shows the full size of the tool, which consists of a steel plate mounted on feet, and pierced with a number of holes for the reception of screws, when taking down a watch. In the center of the index is a hole for the staff, and an oblong slot for the reception of the roller jewel. To get any American movement in beat, proceed as follows: In front of No. 100 is a small spring; push same towards No. 10; then place the balance on top of the stand, with staff in center and roller jewel in the oblong hole; let the spring back gently; the balance will then take its own position. Set degree hand in front of the desired degree, as per direction on index table; place hair spring stud in front of degree hand, and push on the collet.

INDEX TABLE FOR HAIR SPRING STUDS.

_Size._ _Degree._ Columbus 18 Open Face Breguet 23 Columbus 6 Open Face Breguet Elgin 18 Open Face Breguet 66 Elgin 16 Open Face Breguet 52 Elgin 16 Flat Hair Spring 52 Elgin 10 Flat Hair Spring 50 Elgin 6 and 8 Flat Hair Spring 50 Elgin 0 Flat Hair Spring Illinois 18 Open Face Breguet 33 Illinois 18 Hunting 84 Illinois 18 Open Face Flat 89 Illinois 16 Illinois 6 Hunting 52 Illinois 4 Hampden 18 Dueber Hunting 80 Hampden 18 Open Face 75 Hampden 16 Hampden 6 Hunting 50 Howard 18 Old Model 5 Howard 18 New Model 23 Howard 16 Howard 6 Rockford 18 27 Rockford 6 Waltham 18 Key Flat Hair Spr’g 48 Waltham 18 O. F. Hair Spring 61 Waltham 18 Breguet 50 Waltham 14-16 42 Waltham 4-6 50 Waltham 1 42 Seth Thomas 18 Open Face 50 Seth Thomas 18 Hunting 52

=316.= =Oil-cup Drills or Chamfering Tools.= The reservoirs that contain a supply of oil at the ends of pivot holes are made in the lathe with a semi-cylindrical drill, or by hand with a chamfering tool of the form shown at B or C, Fig. 144. A drill gives a clean cut, but necessitates a subsequent polishing of the hole; as to the chamfering tool here referred to, some inconvenience will be experienced in its use, owing to the point being apt to jump out of the hole and make irregular scratches on the brass, which are difficult to remove.

[Illustration: _Fig. 144._]

[Illustration: _Fig. 145._]

The best shapes of drills for making, or at any rate for re-forming or finishing oil-cups, are shown at D and F, Fig. 144, and in Fig. 145.

D and F are two drill-blades that terminate in non-cutting circular arcs. The flat curved end is more and more inclined from the top towards the corner, from _i_ towards the side _e_; the angle at _i_ becoming more acute, and at _e_ more obtuse towards the corners. The drill will, of course, only cut when rotating in one direction; in the other direction the obtuse angles and the reverse sides of the cutting angles will act as burnishers. Thus if the angles on either side are well formed and the blade has been polished, the surface of the oil-cup will be clean cut and polished. F is similar to D, but made from a steel rod.

=317.= _Observations on making the oil-cups._ Reservoirs that are made with a drill, or with a chamfering tool by hand, will often be found to be eccentric, and, when a pivot-hole is bushed and re-drilled, it proves to be struck from a different center from the oil-cup. In such cases watchmakers often give themselves endless trouble without securing a cup of good form and well centered. This difficulty can be avoided by using the tool in a lathe driven by a wheel; then, holding the plate in one hand square against a drill rest in tail stock, advance the tail stock with the other hand so as to bring the plate in contact with the drill.

When it is only required to correct the form of an oil-cup, the drill may be replaced by a rod with file cuts on its rounded extremity (H, Fig. 144). The reader will find no difficulty in making such a cutter for himself, drawing a file with both hands over the rounded end, but always in the direction of the file-cuts. After covering the surface with lines in this manner, rotate the cutter through a right angle and form a number of cross cuts. Or roughen the surface with a chisel of the form shown at H; after making a few cuts parallel to each other, turn the chisel through an angle and repeat the operation.

=318.= =Chamfering Tool.= As is well known, this is used for removing the roughness that a drill leaves at the edge of a hole, or to take off the cutting edge around a screw head sink, etc., thus forming a bevel edge. The tool commonly has a flat semicircular blade, the diameter of which depends on size of hole to be made; this semicircle is ground to a cutting edge like a drill, as shown at A, Fig. 144. Chamfering tools are also made pyramidal, with flat faces, as at B and C; the angle at the apex is more or less acute, according to the depth of chamfer required.

The oil-cup drills D and F are also used for chamfering the edge of a hole.

A cone formed at the extremity of a piece of pinion wire with a cutting edge on each leaf and hardened will be found very useful for this purpose.

=319.= The two forms of chamfering tool first described leave a series of undulations on the bevel edge, so that, instead of being conical, it presents a number of small facets. This inconvenience can be avoided by using the tool shown at Z, Fig. 145.

A small disc of hardened steel is pivoted within a recess formed at the end of a rod, the pin on which it rotates being at right angles to the direction of the rod. As is seen in the figure to right of Z, the section of this roller is a rectangle, and the surface is carefully polished, the edges being left sharp.

Clockmakers make use of a tool for forming oil-cups that only differs from the one above described in two particulars: (1) The disc is fixed on its axis; and (2) the edge, instead of being square to the two faces, is inclined as shown at _j_ and at the same time is slightly rounded crosswise.

A few trials will be found necessary before the most convenient thickness and inclination of edge are arrived at.

=320.= =Hollow Chamfering Tools.= These, as is well known, are used for removing the angles at the ends of cylindrical rods, of steady-pins, etc., or for rounding them off. Three forms are shown at O, Q, N, Fig. 146.

[Illustration: _Fig. 146._]

O is a round rod, the flat end of which has been filed across with the corner of a triangular file. Four cutting edges are thus produced which will act on the end of any object that rotates within them, or _vice versa_. If it be required to form a very acute angle, two slits must be cut with a screw-head file and the sides afterwards inclined to the required extent with a flat file. This tool will serve a double purpose: (1) to chamfer off the edge of a rod; and, (2) by prolonging this operation to form a point at the end.

As a rule, when it is desired to round off, say, a pillar of a clock after reducing its length or from any other cause, a hollow chamfering tool of very open angle is used, a rocking motion being imparted to it round the axis of the spindle; it is better to use a tool of the shape shown at N or Q. The latter, Q, is easily formed by strokes of a rat-tail file at right angles across its end; the other, N, is cut internally with a shaped chisel or with a small rotating cutter to which different inclinations are given during the cutting, as is also done when using the chisel.

=321.= The tool shown at O, Fig. 146, has been modified as follows by M. Roze. The two notches at right angles are replaced by three equidistant notches of equal depth. To make these in a piece of round steel it should be divided on the circumference into six equal parts; then cut the three notches as follows: Calling the points marked on the circumference 1, 2, 3, 4, 5, 6, one notch will lie parallel to the line joining 1, 3, and equidistant between this line and the point 5; a second will be parallel to 3, 5, and midway between that line and point 1, and the third will be parallel to 5, 1, and midway between this and the point 3.

In a hollow chamfering tool thus constructed it will be found that only the three long sides 1, 3, 5, actually cut, and at 2, 4 and 6 are short sides that are set back. But when a file is laid on the face joining two of the former sides, say 1, 3, the short faces 4, 6, will protect the cutting edge 5 from contact with the file.

=322.= =Tool for Centering Rods.= These appliances are well known to watchmakers, who often employ them for marking the position of the hole in the brass wire when making bushings. It is advisable to have such a tool somewhat large, about a third as large again as that shown at _s r_, Fig. 147.

[Illustration: _Fig. 147._]

The head of the centering punch or drill is filed flat on either side, and this flattened portion passes into a notch in the spring _r_, which maintains it in position and prevents rotation when the triangular-pointed blade is pressed against the end of this rod, this rod being caused to rotate in the hollow cone of _s_. Instead of a spring such as _r_, a helical spring is often used; but it then becomes necessary to fix a pin in the drill that slides in a groove in _s_, so as to prevent the drill from rotating.

=323.= =Centering with a Set-Square.= The set square may be used for centering round rods, and the following is a very simple mode of applying it:

[Illustration: _Fig. 148._]

On one arm of the square R, Fig. 148, a triangular plate _c d_ is screwed or riveted so that its edge _c d_ exactly bisects the right angle, that is, divides it into two equal angles. The flat end of a round rod is held within the angle and against the plate, a line being traced on it along _c d_; it is then turned through about a right angle and a second line traced. The intersection of these two lines gives the axis of the rod.

=324.= =Tool for Roughing Out Points.= This is merely the inverted chamfering tool of which two forms are described in paragraphs =320-21=, one of them being also shown at O, Fig. 146. It will be evident that when the end of a rod is caused to rotate in this hollow cone it will take its form.

In some cases it may be found convenient to place such a tool in the tail stock of the lathe.

If the bottom of the cone at the end of O were prolonged by continuing the cuts farther down with a thin flat file, the point of the rod might be formed like a conical-headed screw before it is tapped.

=325.= =Balance-spring Collet Tool.= This convenient little tool for rotating the balance-spring collet is commended almost as much by its simplicity and facility of construction as by its usefulness.

[Illustration: _Fig. 149._]

A steel rod _n_, Fig. 149, is fixed in a handle T; it terminates in a cone _a_ and is drilled with a fine hole as indicated by the dotted lines. A thin wing _b_, pointed at its extremity, is also attached to the handle.

Holding the balance between the fingers of the left hand and the tool in the right, the blade _b_ is introduced into the slit in the collet while _a_ rests on the balance staff shoulder, the pivot being within the hole _n_. Now rotate to the right or left until the stud is opposite to the mark on the balance rim, and this may be done without danger, providing the tool is held firmly and vertical.

[Illustration: _Fig. 150._]

=326.= =Watch-hand Holder.= A very convenient form of tool, in which to clamp a hand while enlarging the center hole is represented in Fig. 150. Two brass plates, _f_ and _g_, are hinged at _m_ like a sector. A collar, _a b_, surrounding the two is pivoted at _a_ and has a clamping-screw _b_ by which the two plates can be forced together. Several circular sinks of different sizes and equally divided between the two plates, are cut of a depth varying from one-half to two-thirds that of the plates, and they must be made to increase in diameter as they get deeper, thus resembling the internal groove that receives a barrel cover. The plate _a_ is cut away along the portion _c d_ and grooves are formed to leave passages open between this surface and the bottom of the sinks in _g_ and _f_.

When it is required to enlarge the hole of a watch-hand, place it, inverted, in the hole of suitable size, as shown at _c_ of the figure, and tighten the screw _b_. Held round the whole or greater part of its circumference, the hand is thus firm and its center hole can be enlarged without risk, either with a drill or broach; the hand will not show marks due to the pressure with which it has been held.

=327.= =Common Hand fitting Pliers.= The sliding tongs with large flat head, perforated with a number of holes in which the head of a hand is clamped when the opening requires to be enlarged, are often useful, but we feel them to be less so than the holder just described. It is desirable that the inner faces of their jaws, which are usually left rough, be at least smoothed.

[Illustration: _Fig. 151._]

=328.= =Another form of Watch-hand Holder.= M. Fiquemont has devised the simple little tool shown in Fig. 151. It consists of a short brass rod R, perforated lengthwise and having a thread cut externally on the surface _a b_. It should be reduced in thickness below this tapped portion. The rod, shown also in longitudinal section at P, is cut into four quarters by two slits from _a_ to _b_, which are at right angles and leave the points as indicated apart at _d_. The elasticity of these four quarters should make them take the form of a reversed cone when holding a hand, so that the ascent of the screw _c_ shall tighten them.

Within the head _a_ of the tool is formed a circular recess, so that, if the reversed head of a watch-hand be placed within it and the screw made to ascend, it will be held very firmly by the circumference, as seen in the figure. The hand will thus be perfectly free to adjust in any way that is needed for fitting it while held at the end of the tool, and without being removed before the work is complete. Three or four sizes will suffice for all ordinary watch-hands.

A tool may be made in a similar manner, except that the screw is not divided by the longitudinal slits, and the hand is held against the point by a lantern (similar to those of a screw-point tool), which must be cut away in the manner indicated in Fig. 150, explained above (=326=). An assortment of three or four lanterns will render the tool serviceable for all sizes of hands.

[Illustration: _Fig. 152._]

=329.= =Clip for Holding Escapewheels while Cleaning.= A mere inspection of M, Fig. 152, will make the arrangement of this little tool evident. The fork is made of a piece of brass rod and its two arms are elastic, a handle being screwed into the lower extremity.

Two small steel jaws are fixed to the upper ends inclined towards each other, and, in using the tool, it is only necessary to press with two fingers on the heads of the screws, when the jaws will open. Having placed the escape wheel pinion between them, the wheel will be firmly held so that its teeth can be easily cleaned, etc.

[Illustration: _Fig. 153._]

=330.= The appliance shown in Fig. 153 can be used for a similar purpose, and is further especially serviceable for holding an escape-wheel that is not riveted to its pinion. It consists of two parts, a handle T, shown separate at _t_, which is drilled throughout its length and tapped externally at the portion _t_, and a collar or nut D, the end of which is traversed by two cuts at right angles that resemble the letter =T= in section. If the tool is intended for holding escape-wheels that have three instead of four arms, this cross must be replaced by three radiating grooves of similar section. The position occupied by the wheel is indicated by the dotted lines _r r_, and it will be evident that, when the flat end of T is screwed up against this wheel, after dropping it into the cross and slightly turning round the axis as in a bayonet joint, it may be firmly held. The safest mode of introducing the wheel is by holding it on a broach, which is subsequently removed.

[Illustration: _Fig. 154._]

=331.= =Tool for Testing the Truth of a Cylinder Escapewheel.= The small tool shown at D, Fig. 154, can be advantageously used in place of the plain arbor commonly employed for testing the equality of the spaces in such a wheel. The plate D, which may be mounted on three feet, is traversed at its center by the smooth conical portion _f_ of the screw _f v_, tapped somewhat tightly into a cock fixed to the other side of the plate. There is a radial slot, _a c_, cut in the plate large enough to allow an escape-wheel pinion to move freely. An inspection of the figure will make evident the manner in which the tool is to be used: a wheel being placed as shown, or with reverse side upwards, is made to slide towards the center, gradually raising the screw until the largest space is found to admit _f_ with contact at both sides. All the smaller spaces are then carefully opened until they admit the cone in the same manner as the largest.

=332.= _Novel tool for the same purpose._ When the spaces are adjusted in the manner explained above, or if the length of the teeth is measured in a narrow gauge plate, there will nearly always remain a certain degree of irregularity in the teeth. A more efficient means would be for the gauge to embrace both a tooth and space, and this condition is satisfied by the following appliance.

[Illustration: _Fig. 155._]

The slide _k k_, Fig. 155, is dovetailed into a plate, level with its surface, so that _k k_ can be moved in a vertical direction by a screw; it is perforated with a series of holes of gradually decreasing diameter. To the same plate are also fixed: (1) a smooth tongue, _b_, with a foot and screw; and (2) a second tongue, _j_, terminating in an index _x n_, which is movable about a pivot, _x_, and held against a pin in the plate by a light straight or spiral spring. The extremity, _n_, traverses a graduated arc.

Having introduced the pinion of the wheel, or the arbor on which it is held, into a hole of the slide that it fits without shake, and brought this hole to the position indicated in the figure, apply a slight pressure to the wheel in the direction of its rotation. With one tooth resting against _b_ the tongue _j_ will be held by the spring against the next and the reading of the index is to be noted accurately. Withdraw the wheel slightly, and, placing the succeeding tooth against _b_, take a second reading, and so on around the entire circumference.

Of course, the delicacy of the instrument will be increased by lengthening _x n_ in comparison with _x j_.

[Illustration: _Fig. 156._]

=333.= =Tool for Removing Studs.= Fig. 156 represents a small tool which may be employed for this purpose. It consists of a thick strip of metal, C, spreading out like the letter T at the end which is not shown, so as to form two feet, the screw, _j_, being a third, so arranged that the T rests horizontally. The disc, _d_ (shown also in plan), rotates on the screw, _j_, and is partially enclosed in a horizontal slot. Around the circumference of _d_ are four rectangular notches of different sizes. The holes indicated by black dots on the plan receive the point of the screw, _v_, which clamps the disc when the notch corresponding in size with the stud to be removed has been brought under the small cone projecting from the spring, _b_; the other end of _b_ is fixed to the T-shaped piece, C. The mode of using this little instrument will at once be evident. Resting the right arm on the bench, and, with the left-hand, bringing the wing of the cock above the notch in _d_, the other hand presses upon the milled button of _b_, forcing the conical pin against the stud and thus removing it from the cock. The screw, _a_, can be adjusted so as to prevent too great force being applied.

[Illustration: _Fig. 157._]

=334.= =Tweezers for Removing Studs.= One form is shown in Fig. 157. The upper arm, H, is bent downwards as indicated at _g_. The lower arm is shorter and carries a separate piece, _n m_, which slides under two screws, _s_, and is pressed forward by a spring, _r_. The action will be easily understood; the extremity, _m_, rests against the stud, and _m n_ is forced backwards until the point, _g_, is exactly over the stud pin. A simple pressure of the finger will then suffice to remove the stud.

A still more simple pair of tweezers for this purpose may be made by filling a square notch in the end of one prong of an ordinary pair with broad noses, and setting a pin opposite to its center in the end of the other prong.

=335.= =Staking Tool.= The modern staking tool will perform the same work as the last two tools described and many other operations. It consists of a shifting table, around which holes of various sizes are arranged in a circle, so that any desired hole may be brought under a suitable punch moving in a vertical holder. Usually twenty-four tempered steel punches and four stumps are provided, which will be found sufficient to cover all the operations in the ordinary run of watch repairs, and the ingenious workman can from time to time add to these by making punches in his spare moments, if he finds from experience that he is in need of punches of a different shape. Fig. 158 illustrates the Johanson combination staking tool, on the front end of which a hairspring stud indicator is arranged.

[Illustration: _Fig. 158._]

=336.= The staking tool can be used as a cannon pinion tightener by making a punch for it having a blunt chisel edge. When a cannon pinion is placed on a stump which is slightly dished in that portion of its face opposite to the punch, and the punch gently struck with a hammer, it will be sufficiently contracted to insure the requisite adherence to the set-hands arbor. If fears are entertained lest the pinion should be cracked with the blow, it may be placed loosely on an arbor and held in position.

=337.= It may also be used to advantage for tightening the set-hands arbor in the center or cannon pinion, but care must be exercised or the arbor may be bent so that the minute hand which it carries passes nearer the dial at one place than another.

An arbor that is too loose is introduced into a suitable stump and at the top and bottom of the slack portion two punch marks are made opposite one another. The punch having a conical or three-sided point, will occasion an expansion of the metal round each mark; if a smooth file be passed over the surface so as to remove the burr, which would not offer any permanent resistance, sufficient projecting metal will be left to secure a sound and lasting friction when a little oil is applied.

If the arbor is well supported immediately beneath the punch, it will not be distorted by any moderate impact. It is advisable before operating on the metal to ascertain its degree of hardness.

=338.= It may also be used as a pinion riveting tool. The pinion, with its wheel in position, is placed on the hardened steel stump, the end to be riveted being upwards. The riveting is then struck with the polished end of a hollow punch. If it be required to spread the riveting, a punch must first be used that is rounded from within outwards, to be followed with a perfectly flat punch. A little practice will at once enable a workman to select the best form of punch.

The stump should be very hard and polished, funnel-shaped downwards and carefully fitted to the bed, so as to be firm and central with the punch. If these precautions are not taken the pinion will spring and the riveting will be imperfect.

=339.= The staking tool may also be used for closing up barrel holes, screw-holes, etc. In repairing watches it is often found that the screws hold badly or not at all, and the holes at times cannot be satisfactorily bushed. In such cases it becomes necessary to close them, an operation which any intelligent workman can perform very well in the following manner: Make a stump rounded at the top and provided with a pump-center. This can be merely a pointed steel rod that passes through the stump from below with slight friction, and is forced upwards by a light spring fixed by a screw, so that, on undoing the screw, the rod can be removed. The one pump-center can be used for various stumps as the openings are funnel-shaped downwards. Center the hole to be closed by means of the pump-center, then bring down the hollow punch and strike it as in riveting a pinion. A small circular groove will be formed around the hole, which, if the punch is in good order, will be perfectly even. The form of the punch is very important; the watchmaker must decide for himself by trial as to the most convenient shape. The thickness of the ring of metal may be modified; it is rounded off in a semicircle by some, and curved inwards or outwards by others.

Instead of a pump-center below we have used punches that were themselves provided with a pump center and helical spring. Either form gives satisfactory results.

The holes of barrels can be closed with a punch that is only depressed at its center enough to avoid the point of the pump-center. When the face is more or less rounded the hole will be closed by forming a cup as with a chamfering tool. The tool may then be enlarged if requisite with a round broach or an arbor covered with white wax. It will thus be hardened, and the cup-shaped recess will serve to retain the oil, while the somewhat thinner hole will probably be in a condition to resist friction as long as formerly.

When the hole is of moderate thickness, and it does not require much reduction in diameter, this method will be found satisfactory; barrels that have been thus treated have been found to stand ten years without appreciable wear. When the metal is thicker, however, the spreading inwards is very slight, and there is some danger, in using a round broach to do it, of straining the metal or detaching the central ring of the barrel or its cover.

It should be observed that the methods explained above are absolutely useless for closing pivot-holes, and should only be resorted to for barrels, on an emergency.

=340.= =Drifting Tool.= This appliance, shown in Fig. 159, is very useful for making holes of round, oval or square, or, indeed, any required form. It takes the place of a punching machine for light work.

[Illustration: _Fig. 159._]

The punch, or “drift,” is screwed into the stock C C′. A pin, _p_, fixed in C C′ prevents its rotation while allowing an end motion along the slot _m_ _n_. The end C′ is hollowed out to receive the point of a screw, B, and a pin, shown near C′, is received in a groove turned in B, thus enabling it to draw the stock in the direction C C′. The part H is gripped in the jaws of a vise, and a strong handle, E, is used to advance the screw B B′. With a tool about three times the size of the figure there is no difficulty in punching the eyes of mainsprings, square holes in stop fingers, etc., and it can be made by an apprentice. Of course its strength depends on the pitch of the screw and the radius of the handle E.

=341.= For heavier work it will be necessary to resort to the punching machine. There are several constructions in use, but the most usual is essentially the same as that of the tool just described. The screw works vertically in a strong bridge that is fixed to the bed in which the counterpart of the punch is held. Great use is made of this machine in factories at the present day, almost every part of a watch being in the first instance roughly shaped by its means. Indeed, thin metal is often left as it comes from the punch, and very perfect crossings of wheels, etc., are thus produced.

Steel does not cut well in the press unless it is soft and homogeneous, and the final dimensions of the object can be more nearly approached according as these conditions are satisfied. Attempts have been made to cut levers, etc., of the exact dimensions required, but it is better to leave a slight excess of metal to be afterwards removed by a mill cutter or other means. The crossings of steel lever and cylinder escape-wheels are punched out, but the metal used is of special excellence. Before introducing a piece of steel into the press it is advisable to remove any scale, etc., by pickling, or with a file.

=342.= =Draw-Plate.= Every watchmaker should possess a plate for drawing round wire so as to be able to obtain it of any required diameter. They are to be had at all material houses. In bushing holes in a brass plate, it not unfrequently happens that the brass used for the bushing is not of the same color as the plate. To avoid such a difference cut off a piece from a plate of the same color and round it by hand, making one end to taper. Fixing the draw-plate in the vise, pass this end through one of its holes, and, gripping it in the hand-vise, pull the brass through the plate. Continue this operation through successive holes until the requisite thickness is attained.

No special precautions are necessary, further than keeping the holes well greased and annealing the brass from time to time so as to counteract the hardening caused by the operation.

Such a plate can also be used for steel wire, and plates with holes of special form, for example those for drawing click and pinion wire, are well known in the trade.

[Illustration: _Fig. 160._]

=343.= =The Grammaire, or Dividing Plate.= This tool is shown in Fig. 160. To mark out the crossings of a wheel, etc., fix it by the conical-headed screw _t_ to the middle of the plate, on which are traced a series of concentric circles (not shown) divided into 6, 8, 10 and 12 equal parts. By laying the little ruler _r_ _r_ over the wheel blank and using these division marks as a guide, 3, 4, 5 or 6 radii can be drawn to serve as guides for cutting out the arms.

If it is desired to indicate the width of the arms instead of a mere central line, a series of holes must be drilled at the division marks and screws with tapered points tapped into them from below. Resting the ruler against these cones, the arms can be drawn of any required width, according to the distance to which the screws project. No further explanation is necessary, for the figure shows: (1) a grammaire adapted to mark out a four-armed wheel, these arms being indicated by the dotted lines; and (2) the small ruler _r_ _r_ cut away at the middle so as to avoid coming into contact with the conical-headed screw.

[Illustration: _Fig. 161._]

=344.= =Jewel-resetting Tools.= Hopkins’ patent jeweling and staking tool, shown in Fig. 161, is an ingenious device, and one that will be found very useful to the watch repairer. As the spindle, or handle, to which the cutters and burnishers P P P are attached, is sustained in upright position when in use, by the long bearings through which it passes in the upright F, independently of the lower center, the hole to be cut may be centered either from above or below as preferred; and the depth to which it is desired the cutter shall work is regulated by adjustment of the sliding collar E, and this being a correct uprighting, as well as jeweling tool, with it a pivot hole, or a jewel setting, the correct center (upright) of which has been lost, may readily be corrected, or its true center again found, and, what in some cases would be a very desirable consideration, by careful manipulation with the cutter, which is under perfect control of the operator, the position of jewel settings may be changed so as to alter the depth of locking of the wheels to any desired extent. To regulate the depth to which it is desired a cutter shall work below the surface of a plate, lower the spindle D until, when moved out sufficiently far, the end of the cutter will rest down on the top of the plate to be operated upon, and fasten it there by lightly tightening the screw K; this done adjust and fasten the collar E on the spindle D, to the same height above the top of the upright F as it is desired the cutter shall work below the surface of the plate on which it now rests. This, when the spindle D has been again set free by loosening the screw K, will of course allow the cutter to sink into the hole to be operated upon to the exact distance the collar E had been set above top of F. In adjusting the collar, E, the graduated wedge No. 4, or the jewel to be set, as preferred, may be used as a gauge. The burnishers, No. 9, are used both for opening and closing settings; the same burnisher, having chosen one of proper size, is used for both purposes; the side being used for opening the setting, and the beveled and rounded end for burnishing it down again over the jewel. The pieces 13 and 14 are made to fit in the lower end of the spindle D (the cutter P having been removed), same as an ordinary drill-stock, and are used for burnishing the edges of a jewel setting down flat over the jewel, countersinking screw heads, giving end-shake to wheels, etc.; and being easily made, any one owning the tool can make these for himself, of forms and sizes to suit the particular work in hand. For uprighting purposes, withdraw the spindle D and substitute No. 5, the rings, No. 3, being intended for laying the work on, on the tool bed. For upright drilling through watch plates, mark the place to be drilled (prick punch it slightly) with the cone point of No. 5; which done turn the spindle No. 5 upside down and rest the upper end of the drill in the countersink in its end, the drill being operated with a fiddle bow acting on a collet placed on its shank for the purpose. For cutting off bushings level with a watch plate, either a cutter of the No. 13 or 14 class, or one of the P cutters can be used. For staking or riveting wheels upright on their pinions, lay the stake No. 7 level on the tool bed (the center M having been fastened down out of the way), and with No. 5 center accurately the hole to be used in the stake, and fasten it there by means of the clamps N; then remove the cone end of No. 5, and place a punch with a hole in its end of the required size, on the part _m_, and proceed as in an ordinary upright staking tool.

=345.= =Tool for Flat Polishing.= A thick brass plate is provided with three strong screws arranged in triangular form (G, Fig. 162), and far enough apart to ensure that, if the plate is reversed and rests on their heads, it will remain flat when moved by hand over a polishing surface.

[Illustration: _Fig. 162._]

The screws should fit tightly or be provided with lock-nuts.

We believe that every watchmaker must be acquainted with this little tool. The object to be smoothed or polished is fixed with shellac or sealing-wax to the middle of the triangle formed by the screws; the level is then adjusted so that, when resting on a flat surface, the object to be polished coincides exactly with it. The polisher (for example, a sheet of ground glass) is charged with oilstone dust or polishing rouge, and the object is passed over it until perfectly flat and smooth.

=346.= For smoothing, it is best to use a large sheet of iron or steel. For polishing, copper or bronze is preferred. Ground glass may be employed for both operations; it must be hard and perfectly flat.

A disc rotating in the lathe or mandril, etc., is often used.

The tool may be inverted and rest firmly on a cork, the polisher being then moved backwards and forwards by hand, and always in contact with the three screws.

It is best to use pith for cleaning the polished surface; in its absence use soap, then wash and dry with a soft linen rag. The object is detached by heating the tool, and is cleaned by boiling in alcohol; afterwards pass through pure alcohol at the ordinary temperature and dry.

=347.= This tool can be employed for polishing small surfaces, such as the end of a rod, of a barrel-arbor or a screw-head, as well as for those of greater extent. But it appears needless to enter into further detail.

Instead of three screws some workmen only use two, at some distance apart. The object to be polished, being placed at the third corner of the triangle, takes the place of the remaining screw.

Lastly, if a band be fitted to one side of the brass plate, as shown at _b_, Fig. 162, and held by two screws, it will often be of service as a clamp for fixing the object, as at _s_.

=348.= Flat pieces can be polished on a revolving lap worked by the foot, being simply held in the hand or in a piece of soft leather; but a certain amount of practice is needed in order to do this successfully.

ACCESSORIES

AND MISCELLANEOUS OPERATIONS TO BE PERFORMED IN THE UNIVERSAL HEAD.

=349.= With a view to simplify the work, we will here give, in a collected form, a number of operations that may be performed in the mandril, or universal head, among which the practical watchmaker will easily be able to distinguish those that can be done in the ordinary lathe; we will also describe numerous accessories that the workman should make for himself, if he is desirous of making his mandril or universal head still more generally useful.

[Illustration: _Fig. 163._]

=350.= Prepare a number of chucks of the form shown in Fig. 163. Some of these carry a small bar with screws, by which an object may be clamped firmly to the chuck, an arrangement which is also shown at A, Fig. 163; others have a hole drilled through their axis; others again have a projecting arbor, etc. They may also be made with a flat face on which to cement objects in the ordinary manner.

[Illustration: _Fig. 164._]

As it is often necessary to have a considerable surface to cement, for example, a watch-plate, one or more may be made of the form shown at T, Fig. 164. The lower plate being clamped in the dogs, the disc _e_ will be free. If this disc be made of bronze or steel it may be used as a lap; if of brass, it may be turned true and used as a wax chuck, etc.

The chucks should, as far as possible, be well made, so that they can be truly centered by means of the pump-center.

TO CENTER AN OBJECT.

=351.= When there is a hole at the center on the side towards the face-plate, in the universal head, as is usually the case, it is only necessary to place this hole over the point of the pump, pressing it inwards, and then to clamp the object in the dogs; the pump is then drawn within the body of the arbor. Very often, however, there is no central hole, or there is only a mark on the face that is towards the cutter; in such a case it becomes necessary to center from the front or by the circumference.

=352.= =To Center from the Front.= If the object is held by wax on a plate, it may be centered as in the ordinary lathe while the plate is hot, by resting a piece of pegwood on the T-rest with a point placed in the central hole, and observing whether its free end remains stationary.

After the plate has cooled, the accuracy of the centering should be tested by means of a long piece of pegwood which rests on the T-rest brought close up to the object. The pegwood is held parallel to the lathe-bed, and, if the centering is satisfactory, its outer end will not move. The detection of any slight movement is greatly facilitated by placing some fixed object close to the free end of the pegwood. If a motion is still observed the centering is imperfect, and must be corrected in the manner explained below (=354=).

=353.= _Perrelet’s method of Centering._ In principle, this is identical with the one just described; but the pegwood index is replaced by the small apparatus shown in Fig. 165.

[Illustration: _Fig. 165._]

A hollow cylinder, of which _a c c a′_ is a section, is firmly held by friction by its portion a _b b′ a′_ in the tailstock. In the front of this cylinder is fixed a steel ring that is thick at the circumference and tapers inward, so that the central hole has a cutting edge. The two black triangles represent a section of this ring. The rod _r_ _n_ passes without play through this hole, and carries a projecting ring at _s_ to determine the distance to which it enters the collar _c c_; there is also a small key that corresponds with a nick in _c c_, and thus prevents rotation.

An inspection of the figure will show that, when _s_ rests against _c c_, if the finger be placed on _r_ and communicate motion to it, the rod _n r_ will be able to oscillate in any direction, and to an extent limited by the diameter of the hole in the cylinder.

The error in the centering at _r_ will be multiplied at _n_ in the proportion of _n s_ to _s r_; thus if _n s_ is ten times _s r_, the motion at _n_ will be ten times as great as the actual error at _r_.

=354.= The instrument is used as follows: The object to be centered being placed between the jaws, having the centering spindle in position in tailstock. Slide tailstock towards the face-plate until the point _r_ of the rod enters the hole, or central mark of the object, and, setting the T-rest close to the point _n_, rotate the face-plate. If the centering is exact, the point _n_ will remain stationary. If _n_ moves to and fro, give a gentle blow against the edge of the object, which should not be held firmly in the dogs; the blow must be on the side opposite to that at which _n_ shows the greatest deviation from the point of reference. Repeat the process until the centering is perfect or sufficiently accurate; then clamp the dogs firmly, taking care not to disturb anything.

In centering from a jewel hole, an aluminium rod _n s_ may be employed on account of its lightness, and it may be terminated in an ivory cone at _r_.

=355.= There is one precaution to be observed, as it facilitates the use of this appliance; it is advisable that the portion _a b b′ a′_ of the cylinder be somewhat long and well made, in order that, while being in the first instance inserted in tailstock up to the shoulder, the cylinder may be partially withdrawn and still held firmly. The reason for this is as follows: When the tailstock is pushed along, a considerable amount of friction resists its motion, and, as the hand cannot always control this motion, it may happen that _r_ comes up against the object with some force. To avoid this, bring the point near the hole and then rotate the collar in the tailstock so as to gently withdraw it to the requisite amount. The cylinder may, if desired, be fixed by a small screw after the point _r_ has been set in position.

[Illustration: _Fig. 166._]

=356.= =Another Centering Device.= The centering indicator shown in Fig. 166 will also be found useful for testing for exact center. The body of the indicator is made of sheet brass, and should be about five inches long by two inches in width at the larger end. The shank _C_ is made to fit in rest holder, and is either riveted or soldered to the body; _R_ is steel or copper wire sharpened to a fine point, and balances on a pivot at 1; _B_ is a clock hand pivoted to the body at 1; 2 and 2 are pivot joints only, and do not go through the body; _C_ will perhaps give a better idea of the end _R_. To center with this tool, unscrew your rest and remove it, then place the shaft _C_ in rest holder and adjust it till the needle point _R_ touches the top of hole, as shown at _A_. The index hand will then note the variations as the head revolves. If too low, the hand will point above center, and if high, vice versa.

=357.= =To Center from the Circumference.= Two cases may occur: Either the entire rim of the object is exposed, as when the teeth are to be cut in a wheel blank; or the rim can only be used as a means of determining the center, as when a barrel has been bushed with an undrilled bushing.

=358.= The tool shown in Fig. 166 may also be used for the test if the short end of arm R rests against the under side of the object that it is desired to center.

=359.= When it is required to drill or merely to center the hole in a wheel, barrel, etc., that does not run true, clamp a piece of sheet brass in the dogs and turn out a sink that will exactly receive the wheel, etc., but allowing it to project slightly. Now unscrew one dog and advance it a little, so as to grip the edge of the object as well as the plate; move the other dogs inwards in succession, and it will only remain to drill or true the hole with a suitable drill.

UPRIGHTING AND DRILLING.

=360.= =When the Lathe is Provided with a Tailstock.= Let it be required to mark and drill a pivot-hole in the cock when the plate-hole is accurately centered by means of the pump-center. Place the tailstock in position on the lathe-bed, and mark the position of the hole with a center, as in an ordinary uprighting tool; then, if the hole is to be very fine, make it with an ordinary pivot-drill.

If the hole to be drilled is somewhat large, it may be drilled with the twist drill, the bed of the lathe being, as usual, horizontal.

=361.= =When the Lathe is not Provided with a Tailstock.= In such a case it is possible to upright and drill by using fine drills, and making points so formed as to take the place of the cutter. Or a stock may be made to receive drills, points, etc., and it may be well here to remark that stocks of the same form are convenient for receiving chamfering or sinking tools.

[Illustration: _Fig. 167._]

This stock is shown in Fig. 167. An inspection of E _c_ will suffice to show its form, and it may be used for holding either a drill or a marking point, or a small hollow center in which to support a pivot drill.

The following method should be adopted for securing accuracy in the adjustment of these stocks:

There must be no shake of the stock in the tool-holder; it is especially important to avoid any displacement during the act of clamping. If there is any reason for doubt on this point, drill a hole at the foot of the cutter in which an index, _y_, can be temporarily inserted; any displacement can be detected by its deviation from a fixed mark. As a rule, however, there will be no occasion for doubt if the plate that is screwed down upon the stock is parallel to the bed of the tool-holder.

The cutter is then replaced by a stock of the form shown at E′, in which a hole has been previously drilled to receive the drill or other bit, but somewhat smaller than it is required finally to be. The pump-center must now be replaced by an accurately fitting piece B that terminates in a short semi-cylindrical drill.

It will be evident that if the mandrel be revolved, and, at the same time, the tool-holder advanced towards this drill, the hole in the stock E′ will be enlarged and smoothed, and its axis will accurately coincide with that of B. Any drill, chamfering tool, etc., that has been turned true, will, therefore, on being inserted in the stock, prove to be strictly in the axis of the lathe.

[Illustration: _Fig. 168._]

=362.= =To Drill a Series of Holes.= Mount on a stock similar to that just described, a small frame carrying a drill-stock, as shown in Fig. 168. If this be fixed in the slide-rest in place of the cutter, it can be used for drilling a hole or a series of holes previously marked out, or, if the pitch of the transverse screw of the slide-rest is known, for a series of equidistant holes in a horizontal line. When it is required to drill a series of holes in a circle, as, for example, in the escape-wheel of the pin-escapement, bring the point of the drill onto the circumference and then proceed as when using the ordinary wheel-cutting engine provided with a vertical drill-holder, taking care to fix the face-plate by means of an index.

This index should have a means of slightly modifying its length, so that the point of the drill may always be brought into exact coincidence with the points that have been previously marked on the object.

It will be observed that, if the drill were replaced by a round milling tool, the U’s of a cylinder escape-wheel might be polished, or, indeed, cut, the concave ends of the teeth of the star-wheel in a Geneva stopwork could be corrected, etc. But it is unnecessary further to insist upon the many uses to which this form of tool can be applied.

=363.= =To Cut the Teeth of a Ratchet, Minute-Wheel, Etc.= When the face-plate is divided on the circumference, it is easy to cut the teeth of an ordinary wheel of a timepiece, escape-wheel, barrel ratchet, to cut or true a star-wheel for the stopwork, etc. After mounting the wheel on a chuck and carefully centering it, replace the cutter by a small revolving cutter-frame after the model of that shown in Fig. 168.

The stock _d_, shown in both plan and elevation, carries a piece _c_ at right angles, which has a slot cut throughout its length. In this slot a U-shaped support can be clamped by a nut in any position. The U portion forms a bearing for a cutter, such as is shown at _f_ in the figure, and the axis projects so as to receive a ferrule for rotating the cutter.

It will be evident that, with such an arrangement, the height of the cutter can be adjusted in accordance with the teeth to be cut.

=364.= =To Cut a Circular or Elliptic Groove.= For this purpose no special accessory is needed; an ordinary cutter will suffice.

[Illustration: _Fig. 169._]

Let _a b c d_, Fig. 169, be the form of the required groove. Mark a series of centers so that circles struck from them will just overlap one another, and at the same time nearly reach the edge of the groove. Then turn out all the circular sinks, indicated by shaded lines, to the required depth.

Center the plate by the point _o_ from which the arc _a b_ is struck; now bring the cutter to such a position that its outer cutting edge coincides with the arc _a b_, and bring it against the plate; set the face-plate in motion, not, however, by using the treadle, but by the hand at its circumference, and traverse the arc from _b_ to _a_; then withdraw the cutter. By this means the projecting angles, left white in the figure, will be removed, and a clean edge will be left to the groove.

As an operation of this description will not present any difficulty, further explanation appears unnecessary; for the information above given will enable any watchmaker to make curved grooves of the kind indicated.

If it is required to smooth the surface of the groove, replace the cutter by a pegwood stick that can be rotated with friction, and the end of which just fits into the groove, charging it with pumice or other stone and oil. One hand moves the face-plate backwards and forwards, while the other rotates the stick.

[Illustration: _Fig. 170._]

=365.= _To Cut the Cylinder Escape-Wheel Cock Passage._ As a rule the cock is cemented, inverted, to a wax chuck, and the passage cut or enlarged on the lathe. It is more expeditious to use a plate provided with a clamping bridge, as shown at Fig. 170. The face-plate should be made to oscillate backwards and forwards by hand, and not rotated by the wheel.

=366.= =To Make a Straight Groove.= _First method._ The tool devised by M. Chopard, director of the school of horology at Besançon, and shown in Fig. 171, is used for this purpose. As will be seen, it consists of a small lathe which is adapted to the slide-rest as follows:

[Illustration: _Fig. 171._]

Two pins, _a a′_, are planted in the top of the tool-holder, the cutter together with the plate by which it is clamped having been first removed. Holes drilled in the frame _f f_ fit accurately onto these pins, while a screw, _h_, passing through an intermediate hole, affords a means of firmly fixing the apparatus to the tool-holder M.

This tool should satisfy the following conditions: The arbor C should fit into a recess that receives a cutter, but without coming into contact with it; this arbor should be parallel to the bed of the lathe; and, lastly, the axis of C should be on a line with the lathe center.

=367.= Having set this little appliance in position, trace on the watch-plate two lines indicating the directions of the sides of the groove as well as lines fixing its length. Now place the plate in the dogs, setting the point of the pump-center anywhere on the line drawn along the middle of the groove. Turn the plate so that this line is horizontal, and fix it in any way that is convenient.

The arbor C carries a revolving cutter _k_, which can be changed as desired, and is held in position by the clamping screw _d_. Assume that the diameter of this cutter corresponds exactly with that of the required groove; advance it towards the plate, turning the wheel rapidly, the cord being round the ferrule _b_; a circular sink will thus be formed in the plate of the same diameter as _k_.

When this has been cut to a sufficient depth, the tool is moved parallel to the face-plate, and the cutter _k_, continuing its movement of rotation, will now cut, not with its extremity _i_, but with its sides. It will thus form a straight groove of any desired length.

=368.= The cutter is a three-sided prism, or it may have four sides with four cutting edges on the sides, and only one cutting edge at the extremity _i_. If it is preferred to retain only the two acting edges that start from either end of the cutting edge _i_, they may be made more acute, and the other pair reduced by means of a file.

[Illustration: _Fig. 172._]

=369.= _Second method._ This is simpler than the one just considered. At the end of a rod G, Fig. 172, which takes the place of the cutter in the slide-rest, a plate _p_ is fixed. A line is drawn across the face of this plate in such a position that, when G is clamped in the tool-holder, this line is horizontal, and in the plane that contains the axis of the pump-center.

Let it be required to cut a straight groove in the piece of brass _l_. Wax it to the plate _p_ so that the axis of the required groove is over the line traced on the plate. Now fix G in the tool-holder and replace the pump-center by a rod D, the extremity of which is formed into a cutter of a diameter equal to the width of the required groove; the rod D should be fixed in the hollow arbor by a screw. It is then only necessary to set the cutter in motion, forcing the piece _l_ against the revolving cutter, until the requisite depth is attained. Then, by making the tool-holder travel parallel to the face-plate, the groove will be elongated until of the desired length.

=370.= The cutter may be of the form shown in Fig. 171, or it may be as shown at _b_ in Fig. 172, since the movement is always in the same direction. The cutting edges are each formed by two small inclined faces, one pair of which is shown at _b_; they occupy half the diameter of the cutter. At the back of this pair the cutter presents the appearance of the lower half shown in the figure and _vice versa_.

It will be evident that the two sides of this cutter will act while its motion is continuous in one direction.

Besides the numerous operations that can be performed on the lathe as we have hitherto indicated, it may be employed, if divided on the head stock, for tracing out angles, marking the crossings of a wheel, a balance, etc., and for other purposes, many of which are referred to in the course of this work.

PRODUCTION OF SCREW THREADS.

SCREW PLATES AND TAPS.

=371.= The lathes employed in the manufacture of screws are of two kinds; those intended for polishing and, where necessary, modifying the form of screw-heads, much used by watch examiners and repairers, and those specially designed for cutting the threads, which are mainly in use in factories.

Before discussing them, however, we will give some account of the screw-plates and taps in ordinary use.

=372.= =Common Hand Screw-plates.= The use of these is much facilitated by providing a second plate perforated with holes of such sizes that a spindle which just passes into a hole of any given number will be of the size most convenient for forming a screw in the hole of the same number in the screw-plate. For a long time we have made use of two Latard screw-plates so made that a rod which would enter one hole without play was of the most convenient size for forming a screw in the next smaller hole but one (thus the plate perforated with plain holes can be replaced by a second screw-plate, or by using the successively larger holes on a single plate as gauges).

[Illustration: _Fig. 173._]

In order to form a screw that is clean-cut and even, with the least possible straining of the metal, the holes in the screw-plate should have notches cut as shown at F, Fig. 173; they should be carefully hardened and well polished on each side of the notch, and this system is now even applied in the case of the smallest jewel screws.

=373.= =Screw Dies.= The ordinary plate, in which notches are not cut at the sides, squeezes up and strains the metal. This effect is less marked when separate dies are used, and disappears entirely if only a small quantity of metal is removed at a time, and the cutting edges of the dies are smooth and in good order. In addition to possessing other advantages, this form of screw-plate enables us to obtain at will screws of the same thread and different diameters or of the same diameter and different threads. The dies must be carefully fitted to the slides that receive them. Dies cannot be employed for cutting very small screws.

=374.= =Fine-threaded Screw-plates.= At the present day these can always be obtained at the material stores; but thirty years ago it was not so, and the watchmaker was obliged to make them for himself. The following method was adopted:

Take a screw formed with an ordinary plate, in which the thread is broad as compared with the hollow. If the screw does not satisfy this condition it must be modified thus:

Having ascertained that it runs true, and that it is larger than will be ultimately required, insert it in a chuck in your lathe. The T-rest must carry a smooth horizontal rod of hardened steel.

Rotating the screw, hold a slitting file in the hollow; the file should fit into this hollow accurately, and should be smoothed on its two sides, only cutting with one edge. The bar of hardened steel will determine the depth to which the file is allowed to cut. By this means a screw is obtained that has a thread thick at the bottom. With the graver remove the top of this thread, round off its corners, and harden the screw, filing three facets along its entire length, that make it taper.

The tap, having been thus prepared, is employed for cutting a thread in a piece of steel, not too thick, that has been previously annealed, and in which a hole is drilled of the proper size. The thread of this internal screw will be thin and the hollow proportionately broad.

The plate is now hammered cold with care until the thickness is so far diminished that the thread and hollow are as nearly as possible of equal thickness. Harden it and chamfer the ends of the hole with a conical steel point and oilstone dust. Then clean it and cut a thread on a piece of soft steel which may be formed into a tap.

If the operation has been properly conducted, this tap will satisfy the prescribed conditions, and, when hardened, it is to be employed to cut a thread in a second steel plate, which will be employed as a screw-plate; for that first formed must, in consequence of the hammering to which it was subjected, present irregularities in the hole, and can only be used to cut one or two taps cautiously. It is useless for making screws or tapping brass. (See also =378.=)

=375.= _To Clear a Stopped Hole in a Screw-Plate._ Drill a hole through the center of the piece of metal that fills up the hole, taking care to maintain it central, and to employ a drill that is sufficiently small to avoid all risk of contact with the screw threads. Pass a broach through this hole and, after tightening it with a few gentle blows with the hammer, turn it in such a direction that it tends to unscrew the broken screw, which will in nearly every case, be removed without difficulty by this means.

TAPS.

=376.= Screw-cutting comprises two distinct operations—the formation of a spiral thread on the circumference of a cylindrical spindle, and of a spiral groove within a cylindrical hole to receive this thread.

Taps are made either by means of a screw-plate or in the lathe; we shall presently refer to this second method. Every watchmaker may be supposed to have received, early in his career, instruction as to the cutting of a tap with a screw-plate. Great caution is necessary in the hardening, for if the tap is not true or the metal burnt it will cut badly and be apt to break. Taps are cleaned after hardening with a piece of wood in the lathe or between two hard pieces of pith covered with oilstone dust, and either three or four cutting facets may be made. It is important to avoid the production of a burr in making these facets; a good plan is to make them while the metal is still soft, and to pass the tap through the plate subsequently, as a sharp cutting edge is thereby produced. The facets should be carefully smoothed, and the use of coarse rouge is an advantage.

A tap with three facets gives the cleanest cut and leaves the most space to receive the metal that is removed, but with four facets the roundness of the hole is more certain to be maintained.

[Illustration: _Fig. 174._]

We have seen taps formed as represented at M, Fig. 174, so that the object in which a thread is being cut is loose at the part _o_, when the direction of movement of the tap is reversed. They are also at times made semi-cylindrical, as at G, and work well in the lathe for tapping brass, but we have not tried this form with steel.

=377.= =To Cut a Tap when of Considerable Length.= The following precautions must be observed in order to ensure that a long screw shall be both round and true.

The steel must be of very goad quality, and loose dies should be used in preference to a screw-plate. It is a good practice to employ two pairs of dies (or even more); one to rough out the screw, leaving the thread somewhat larger than it will finally be, and the other to finish after having trued it, and even sometimes lightly turned the surface in places. Very little metal must be removed at a time, the dies should have sharp cutting edges, and a rather large number of threads.

A screw can be made in the ordinary manner in a screw-plate rather larger than is required, then reduced to the requisite diameter, and finished with a plate in which the holes are of the form shown at F, Fig. 173, or in a screw-cutting lathe; in either case, however, care must be taken to avoid straining the metal in its passage through the first plate, on account of the tendency which it then possesses to become distorted in the hardening.

If a micrometer screw is required, that is, a screw of absolutely uniform pitch, it is necessary to apply to makers of astronomical and other similar instruments of precision.

[Illustration: _Fig. 175._]

=378.= =To Cut a Screw of any Desired Pitch and Diameter.= Let it be required to cut a thread on the stem B, Fig. 175, of any pre-determined pitch that already exists in a screw-plate. Turn down the portion _d_ to such a diameter that a screw can be cut on it in this hole, and fit two runners to the lathe of the form shown at G and H. The end of H is drilled and tapped so that _d_ turns freely in it, and a hole is drilled in G to receive the stem B freely, but without sensible play, and a fine notch is cut at _a_.

It will be obvious that if now the ferrule _r_ is caused to rotate, while a fine saw or file is inserted in the notch _a_, a screw will be formed on B of the same pitch as that on _d_, although there may at the same time be a very considerable difference in their diameters. This method may be adopted in place of that explained in article =374= for obtaining a fine-threaded screw.

=379.= =Left-handed Screw Taps.= The manner in which these are made in the screw-cutting lathe will be subsequently explained; in its absence the watchmaker may adopt one of the following methods:

[Illustration: _Fig. 176._]

_First method._ If, when an internal screw has been cut with a right-handed tap, B, Fig. 176, it be required to tap a second hole in the reverse direction, the following plan may be resorted to:

File the original tap B on two opposite sides, so as to give it the flattened shape shown at A in the same figure. Insert the end into the hole to be tapped and turn the tap to the left with the application of considerable pressure, so as to force the tap to bite. When the tap has been passed in and withdrawn there will be found to be a left-handed thread cut in the hole. For, if the tap is turned towards the right, the thread _f_ passes into the groove already formed by the thread _a_; but, if turned towards the left, _f_ will originate a groove into which _b_ will pass, traveling in an inverse direction to that previously given to it.

The finer the thread of the screw, the better is the chance of success, and with a wide thread it is often necessary to recommence two or three times. If a plate or pair of dies be cut in this manner and hardened, they will serve to cut an even left-handed tap.

[Illustration: _Fig. 177._]

_Second method._ Attach a comb to one or two sides of a cylinder, as indicated at F, Fig. 177. This can be used to cut a thread in the piece of metal S, that is either right or left-handed according to the direction of rotation of F, sufficient pressure being at the same time applied to force it into the plate. The pitch of the thread will depend on the amount of pressure applied. This plan is only a modification of the one described above, and, as in that case, success can only be guaranteed when a means is adopted for securing a definite relative amount of motion in F around its axis and S vertically.

[Illustration: _Fig. 178._]

_Third method._ A tap of unhardened steel is filed into a triangular form, C, Fig. 178, and twisted so as to bring the angles _b_, _f_, towards _a_, _d_, etc.; we thus obtain a tap which will serve, throughout a certain portion of its length, to cut a left-handed thread, but the part that is not so adapted, at the extremities, will require to be removed before hardening.

[Illustration: _Fig. 179._]

=380.= _To Make a Left-handed Tap by Means of a Right-handed Tap._ A portion of the right-handed tap is filed off on three faces to the section shown at _b_, Fig. 179, and firmly set in the die _d_ so as to be held in the frame for screw-cutting dies. A second die, _f_ made of brass and having a semi-cylindrical recess opposite _b_ is fitted to the frame. The diameter of this semi-cylinder should be the same as that of the rod on which a left-handed thread is to be cut. Now grip this rod as shown at _a_ by means of the screw _g_, so that it is held between the die _f_ and the block _b_, and rotate the frame or the rod _a_ towards the left; a spiral groove will thus be cut by the thread on _b_. It is sometimes an advantage to cut this thread lengthwise in the manner indicated at _b′_.

[Illustration: _Fig. 180._]

This method enables us to cut a given thread on a rod of any given diameter. From an examination of Figs. 179 and 180, it will be seen that a simple comb of the form of C or D, carefully made by hand and fixed in the place of _b_, can be employed to cut a right or left-handed thread on any given rod; it is advisable, however, that the teeth of the comb be inclined to the axis of the screw, like the thread of an ordinary tap, as otherwise the operation becomes more difficult and success less certain.

[Illustration: _Fig. 181._]

The method may be simplified by taking a brass plate, D, Fig. 181, of sufficient thickness, and firmly setting in it the right-handed tap, _v_, having only filed away two opposite faces before hardening. The rod to be tapped is then introduced with considerable pressure into the hole _j_, and, if rotated towards the left, it will receive a left-handed thread of the same pitch. The notch shown at _b′_, Fig. 179, will facilitate the operation, as a cutting action will take the place of compression.

=381.= M. Gontard has suggested a modification of this arrangement, which consists in forming the die _f_, Fig. 179, so that the original right-handed tap can be embedded in a hole previously tapped in it and filed away on the side towards _b_ so as to expose a cutting edge; and he points out that, by suitably inclining the frame with reference to the axis of the rod to be tapped, the appliance can be used to cut a double or even a triple-threaded screw, right or left-handed. He further draws attention to the fact that in a screw formed in this manner the sides of the thread are smooth and polished, a condition which cannot be secured when either a plate or dies are used.

=382.= =To Increase the Diameter of a Tap.= It sometimes happens that a screw will not penetrate to a sufficient depth, or fits too tightly into its hole, owing to the tap employed being of a less diameter, either in consequence of the hardening, polishing or wear, or through having been formed in a different screw-plate. In such a case the following expedient may be resorted to:

[Illustration: _Fig. 182._]

Make a fresh tap in soft steel and file away two opposite sides so as to give it the section shown at A or B, Fig. 182: after measuring the diameter at several points in its length, hammer gently on the flattened sides. With a little care and by using a micrometer at intervals for testing the alteration in diameter, it will be found that the required increase can be obtained without much difficulty. The tap is then hardened and polished, etc.; indeed, it is best to make a fresh tap.

METHODS OF TAPPING HOLES.

=383.= It is needless to refer to the method of tapping by hand, as it is well known to all practical men.

=384.= =Tapping in the Lathe.= The plate of a watch is gripped in the dogs of a face-plate, the hole to be tapped being centered by means of the pump-center, which is then withdrawn, and a tap held to the hole; the face-plate is then caused to rotate either by the hand resting on its circumference, a slight backward motion being given after each advance, or the motion may be continuous and be given by the wheel. In the latter case, however, the tap must have a good cutting edge and only be held in the hand with the degree of force required to make it cut, so that it may rotate without breaking in case the resistance opposed becomes too great. The tap may be steadied on the T-rest.

=385.= =To Tap with a Mainspring Winder.= The ordinary mainspring winder will, if the click work is removed, be found very convenient for tapping holes, and indeed, for forming the external thread on screws. Having removed the winding arbor, replace it by a tap carefully centered; then introduce its coned end into the hole in the plate, which must be pressed forward while the handle is turned, a short backward motion being given to it at frequent intervals. When the tap is engaged sufficiently in the hole it is merely necessary to maintain the plate at right angles without applying pressure.

=386.= =To Tap with a Bow.= Instead of the mainspring winder, one of the small drill-stocks to be driven by a bow, consisting of an arbor, with a coned hole at one end and ferrule at the other, supported in a frame that is clamped in the vise, may be used. They are to be obtained at any tool-shop.

The bow being on the ferrule and the tap properly centered in the arbor, the hole is held against the coned end and the bow worked with an alternate forward and backward movement; but if the tap has a good cutting edge and the bow is strong (of steel or cane), a hole may be tapped with a single stroke of the bow. After a few trials the method will be found very easy and certain.

A regular and rather slow motion should be given to the bow, which should be long and strong. It is well to ascertain the number of revolutions of the ferrule that correspond to a stroke of the bow, so as to ensure that the tap is not introduced to a greater depth than is required. If it is desired that the screw work easily in the hole, the tap should be moved several times backwards and forwards.

=387.= The little turns here referred to, some of which are perforated throughout their entire length and others only at one end, are very cheap and will often be found useful; they can be adapted to receive drills, broaches, taps, etc.

=388.= =To Tap in an Ordinary Lathe.= In factories it is a common practice to tap the holes in plates, etc., and even to cut the threads of screws in a lathe specially arranged for the purpose. The tools adapted for such work are of two kinds: in some the tap enters to the required depth, when it is immediately arrested, disconnected, and then rotated in an opposite direction; in others, the tap advances to a definite point, and is immediately withdrawn. As a rule, however, the tap remains stationary and the object is caused to rotate.

=389.= =Beillard Lathe for Tapping Screws.= The axis F M, Fig. 183, is perforated throughout its length. At F, the screw-plate G is dovetailed into it. The inner end of the hole in this plate is slightly coned to facilitate the insertion of the brass wire D, and it must be exactly in the axis of F M. A guide B sliding on two rods _c_, _c_, is traversed by the rod D which can be clamped in it by the screw _a_.

By pushing D against the screw-plate at the same time that the handle N is rotated, a thread will be traced on it and it will emerge at _k_. When B has advanced to the point _m_, the screw _a_ is released, B is drawn back, and _a_ again clamped.

[Illustration: _Fig. 183._]

When a long screw, such as X _x_ has to be tapped, the screw-plate is fixed at _m_, and the guide B is fastened on to the portion X. Of course the hole in the screw-plate must always be abundantly provided with oil.

If the screw-plate F is replaced by a plate perforated with a round or square hole, a drill, broach or tap may be substituted for _k_, being clamped by the screw _h_, and the tool is at once available for drilling, broaching or tapping any given hole.

RAPID MODE OF MAKING A SCREW.

=390.= The methods ordinarily adopted by watchmakers are too well known to need description; we will therefore at once proceed to give a special plan recommended by M. Vissiere.

An eccentric poppet-head with boring-plate, Fig. 185, is fitted to the bed of the lathe, the eccentricity being such that the axis of the centers is at the point _a_ on the circumference of the circle _a y_. The conical hole, having a center at _a_, is cut away towards the rim of the plate to the degree indicated in the figure, and its center is so placed that the vertical line _f_ and the radius _d_ are inclined at 120°. The position of the T-rest is shown at _s_, and by bringing it into actual contact with the disc the steadiness of both is increased.

The fixed headstock of the lathe is provided with a runner of the form B, Fig. 184, terminating in a point _m_ at one end and a hollow cone or funnel _n_ at the other end.

Having filed the ends of a rod T, of any required diameter, square and fitted a ferrule, support it between the two cones, _a_ of the boring-plate and _n_ of the runner. Near the end _a_ cut a hollow _r_ sufficiently small to allow the stem to pass through the notch in the hole _a_, Fig. 185. After passing it through, the rod will be supported as shown at H, Fig. 184, so that the rim _e i_ rests against the cone.

[Illustration: _Fig. 184._]

[Illustration: _Fig. 185._]

Further explanation is hardly necessary; after removing the portion _c g_ with a graver, turn down to a point _p_. When making a screw, turn out a second hollow _o o′_; it then only remains to turn off the disc at the extremity, and the screw will be roughed out of the form _c p g v_.

If it is preferred to work with a point at the left-hand end of B, remove the rod after the point _v_ has been turned, replace _m_ B _n_ by a common runner, reverse B, and recommence the operation.

It would be difficult to devise a method for roughing out a screw and making a point that would be more expeditious than the one here described.

SCREW-HEAD TOOLS.

=391.= These are of various kinds: some work by hand and others by a bow. The jaws are brought together sometimes by a sliding ring, and at others by a milled head placed between them and rigidly attached to a pin tapped with right and left-handed threads that engage in the jaws. But neither of these plans is good; the screws are not held firmly and they are rarely well centered; owing to the slight displacements of the jaws.

[Illustration: _Fig. 186._]

A better plan is to arrange, either in the lathe or in the jaws of the screw-head tool (when driven by a bow), a series of chucks of the form shown at T, Fig. 186. They are easily made and tapped, the hole _i_ serving to remove the metal from the inner end of the hole that has to be tapped; such chucks occupy very little space, and, if numbered to correspond with the size of screw, any chuck required can be found without trouble. If the hole becomes too large owing to frequent use, a larger size of tap can be passed through the hole and its number changed.

=392.= A set of such chucks is almost indispensable at the present day to the watchmaker who wishes to repair watches well; for he rarely makes his own screws, as they are to be obtained well made and very cheap at the material dealers, whereby a great saving of time is effected. But their heads are seldom of the proper size to fit the original sinks, and by being provided with such a series of chucks the watchmaker can at once overcome this difficulty, as he can turn the heads down with a graver.

=393.= R, Fig. 187, is an arbor for a screw-head tool that is driven by a bow, and is adapted to receive such chucks, or it can be used in an ordinary lathe, _d_ being supported on a pointed center, and _g_ in a boring-plate, Fig. 188, or in a cone-plate center.

=394.= In this form of screw-head tool the portion A is sometimes perfectly cylindrical, so that the piece V can slide on to it, being clamped by the screw _b_.

This tube V is cut away through about half its length with a notch, as indicated in the figure; bent pieces of hardened steel _c_ and _n_ are screwed to either side of the notch. Screws, _h_ and _f_, provided with lock-nuts, determine the distance between these plates, and when V is in position on A the ends of _c_, _n_, will rest on the screw-head, leaving just sufficient space between them for inserting the file that cuts the slit.

[Illustration: _Fig. 187._]

Hard steel caps of the form shown at M may also be fitted to A, a notch being cut in them to receive the screw _b_. These will be found useful as guides for filing or polishing screw-heads, or the ends of arbors flat, reducing the heads of several screws to the same height, etc.

[Illustration: _Fig. 188._]

=395.= The tool for forming the U-spaces in a cylinder escape-wheel can be easily be converted into a screw-head tool with laps. A glance at Fig. 189 will at once make this evident. A number of chucks are adapted to the arbor A, and in the tube _c c_ either a T-rest or a spindle carrying a lap is fixed.

It will also serve as a tool for drilling; a drill-chuck with drill, _f_, being adapted to A, and the object to be perforated at _b_ resting against a plate that projects at right angles from a slide _d d_, which may be advanced by a screw _g_.

=396.= The modern watchmaker has so little call to cut screws that it does not pay him to purchase a screw-cutting lathe; for a very small sum he can have screws of any thread or diameter cut by those who make a specialty of such work, always provided that he cannot find what is wanted in the material stores. The same thing also applies to fuzees.

[Illustration: _Fig. 189._]

TOOLS FOR CUTTING AND ROUNDING-UP THE TEETH OF WHEELS.

WHEEL-CUTTING ENGINE.

=397.= The machine for dividing the circumference of a wheel, termed the wheel-cutting engine, and one form of which is shown in Fig. 190, is well known to nearly all workmen. The wheel is fixed to a chuck at B by wax or screws, or by the pressure of a hollow cone or “sugar loaf” of steel, to the apex of which pressure is applied by the arm D, or in other ways. The wheel may be centered either by a pump-center within the chuck or by an appliance such as is shown in Fig. 191, except that the arm _b_ is curved and its index much longer. This little addition may be fixed to the frame of the engine in any convenient position.

[Illustration: _Fig. 190._]

The chuck B that carries the wheel is rigidly connected with a large brass plate A A, on which are concentric circles of divisions, and the whole can be maintained stationary by setting the point of the index C C in any desired hole on the division-plate. The cutter is carried on an arbor (shown separate at L) between horizontal bearings in the frame J, and is caused to revolve by means of the pulley K. The several parts lettered E, F, G, H, are for bringing the cutter against the wheel and modifying the direction in which it moves, so that the machine can cut straight or inclined teeth, bevel or crown wheels, etc. It should be added that the engine here represented is more complex than those ordinarily used for cutting watch wheels, although the principle on which it acts is the same.

The teeth may be cut by circular cutters of the nature of files, by a small straight cutter, similar to those used in a slide-rest projecting from a rotating axis, or by several such cutters mounted on a disc which is caused to rotate. For the sake of distinction it will be well to refer to the first of these as _file_ or _mill cutters_, while the second and third may be termed respectively _single_ and _multiple blade_ or _composite cutters_.

[Illustration: _Fig. 191._]

Watchmakers rarely possess a sufficiently large assortment of file-cutters for making all the various forms of teeth that are met with in horology; but this deficiency can be supplied by making them for themselves to any required pattern in the manner subsequently described.

=398.= _Observations._ The wheel-cutting engine in which the plate is caused to rotate by means of a tangent screw is usually the most accurate. If the pitch of the screw is fine it will give all the subdivisions of a circle that are required for ordinary work, but it is essential that a good form of counter be attached to the screw, and a certain amount of calculation is always needful.

The engine that has a division-plate with conical holes arranged concentrically over its surface is simpler and better adapted for rapid work. The larger this plate, the greater is its chance of being correct and, at the same time, it affords room for a larger number of divisions.

It is preferable that the cutter frame rise and fall in a vertical dovetail, for when the arbor is carried in an H shaped arm pivoted on two screws, the teeth are always slightly dished. The entire apparatus should be somewhat heavily constructed and supported on a solid bed; so as to prevent the vibration of the cutter-arbor from being distributed over the entire machine.

The highest numbers on the plate should be used whenever it is possible, so as to diminish the error due to irregularities in the sub-division. For example, in cutting a wheel of 30 teeth, use the 90 or 120 circles, taking every third or fourth hole.

These remarks will probably be sufficient to enable any watchmaker who possesses a wheel-cutting engine to employ it with success; we will, however, add the description of a few appliances or processes that have a bearing on this question.

=399.= =To Divide a Wheel so that it has one Tooth more or less than any given number on the Division-plate.= It is to be observed that neither this nor the following method is mathematically exact, but if it is practiced with care and the division-plate is of sufficient diameter, the error may as a rule be neglected.

[Illustration: _Fig. 192._]

Let P, Fig. 192, be a division plate that has a 30 circle, but not one of 29 or 31 divisions. Divide the circumference of a disc _d_, seen on edge, into a large number of parts in the engine, 360 for example, and fix it to the end of the index, at the same time attaching a finger, _i_, to the support _s_. Now advance the screw of the index through a distance corresponding to the angle _l_ P _k_ included between the two successive points of the 30-division circle. To measure this distance a pointer should be previously fixed to the frame to correspond with the middle point of a hole in the circle under consideration, and the motion should be arrested when it coincides with the next succeeding hole. Assume that this amount of displacement has required three complete turns of the screw; 1,080 divisions on the disc have thus passed under the finger _i_. Dividing this number by 31, we obtain 34.83.

After observing the division on _d_ that coincides with the pointer _i_, cut the first space of the wheel; then cause 34.83 divisions to pass under _i_, in such a direction that the plate is drawn with the arrow, and transfer the index to the next hole of the circle, rotating this time opposite to the arrow; the second space can now be cut, and so on.

With a view to diminish errors arising from the omission of fractions, since 31 does not divide evenly into 360, a number of multiples of the number 34.83 should be determined. Thus 4 times 34.83 is 139.32, so that, when the fourth space is cut, the pointer _i_ must be at this number of divisions from its initial position.

The index should be so situated that, when half the arc _l k_ has been traversed, as explained above, _s a_ is at right angles to the radius P _r_ of the division-plate. If it is desired to move _d_ in a reverse direction, it must be moved backwards to a considerable distance and then forward up to the required point so as to avoid error due to backlash. The screw of the index should fit the support s firmly and without any shake.

=400.= =To Cut a Wheel with any Given Number of Teeth.= When the given number does not occur on the division plate, proceed as follows: Take a strip of metal, for example a pliant piece of soft steel, and cut in it a series of equal and equidistant notches as shown at B, Fig. 193. Cut the band to such a length that it has the same number of pairs of teeth and spaces as the wheel is required to have teeth. Now turn a lead disc of a diameter that the strip of metal will exactly enclose; fix this strip round the circumference with pins, screws, or in any convenient manner, as is shown at C. We thus obtain a temporary division plate which can replace the permanent one or be attached to its upper or under surface, and, when an index has been adapted to it, the wheel can be divided into the requisite number of parts.

[Illustration: _Fig. 193._]

When employing an engine the division plate of which is worked by a tangent screw, the above affords an easy means of making the divided head for the screw with any desired number of divisions.

=401.= With a view to insure accuracy, it is advisable to employ a disc of large diameter as the errors of division are thereby rendered less important and the metallic blade can be made to lie closer to the rim.

The blade is subdivided by a saw to which a guide is attached as indicated at H, Fig. 193, or the saw can with advantage be replaced by a file that only cuts on its edge and not on either face, or by a pair of mills or revolving cutters united together as shown at S. The following plan, however, appears to be more expeditious and to involve less trouble to ensure accuracy.

[Illustration: _Fig. 194._]

A hole _a_, Fig. 194 is drilled in a metallic band by means of a semi-cylindrical drill fixed in the chuck of a lathe or in a wheel-cutting engine, etc. It will be convenient if the drill can be set vertical. Beneath it is a brass bed-plate in which are fixed two pins equal in diameter to the hole _a_; this hole having been placed over one pin _b_, the band is held firmly against the other, while the second hole is drilled. This is then transferred to the pin, and so on.

In the absence of a suitable tool, a well made measure can be employed for marking a series of points with the aid of an eyeglass; the holes are then drilled with the bow or in any other manner.

=402.= =To Cut a Wheel, Ratchet or Pinion on an Ordinary Lathe.= When only a moderate degree of accuracy is required, the ordinary lathe can be adapted for cutting the teeth of minute wheels, ratchets, pinions, etc., by making the following appliance:

The piece B, Fig. 195, provided with a stud at _p_, slides on two horizontal and parallel cylindrical rods fixed to the slide C, or it may move in a dovetail. The cannon _d_, carrying a ferrule _k_ and a file-cutter _f_, rotates on the foot at _p_ without shake; and the cord of a wheel or bow passes round _k_.

[Illustration: _Fig. 195._]

R, the wheel to be cut, is supported between the runners, the divided plate V, which may even be an old wheel with the required number of teeth, being fixed to the axis of R. V is held stationary during the operation of cutting, by the index _l_. The mode of action hardly requires explanation: while _f_ is rotating, advance B until it is arrested by the stop _t_; then draw B back, advance _l_ to the next division on the plate, and so on.

=403.= We have said enough on this subject to enable any watchmaker to make such a tool, modifying it or completing it according to his requirements. We would only remark that: (1) If a cannon of the form _d_ is used, the stud should be diminished in diameter at its middle part for about three-quarters of its length, so that friction occurs only at extremities; and (2) if a wheel is used to rotate _k_, there should be an idle pulley at _m_ supported on a fixed arm independent of B, either attached to the lathe-bed or bench, or fixed in the vise, so that the ferrule _k_ can move backwards or forwards without altering the tension of the cord, in the manner indicated at Y.

=404.= =Wheel-cutting Arbor-chucks.= These appliances are specially useful in making wheels that are required to be rigorously true, such, for example, as escape wheels. The form is represented in Fig. 196.

It is simply the arbor of an ordinary lathe, formed in two pieces, _b a_ and _b c_, the body _b d_ being very accurately fitted into the conical hole in the plate of the wheel-cutting engine. If now a wheel is fixed with wax on the extremity _z_ and turned in the lathe to the required form, it is only necessary to unscrew _b c_ and introduce _b d_ into the socket of the wheel-cutting engine; then having cut the teeth, the piece _b c_ is replaced, and the whole is set in the lathe, if required to test its truth, without the wheel having been displaced from the chuck.

[Illustration: _Fig. 196._]

It will, of course, be evident that the two parts must be accurately fitted together; the tapped hole and the screw must be true with the axis. M. Millot, with whom we have seen this form of arbor in use, has not been able to detect any eccentricity, although he often employs them.

=405.= They might be formed in one piece, as _a d b_, with a point at _p_. A boxwood ferrule is then fitted onto the portion _b d_, where it is clamped by two screws, and these can be released when it is desired to insert the chuck into the wheel-cutting engine. The points of these screws should be received in recesses in order to avoid the production of any roughness on the surface of _b d_.

Wheel-cutting engines have been made to receive these arbor-chucks without removing the pulley. The point _c_ is placed in a hole and the upper end is enclosed in a collar, which is tightened by means of a screw.

The arbor used by M. Millot had a lantern chuck, and this is very convenient in making objects that require to be measured during the progress of the work.

=406.= =Modification of the Ordinary Arrangement for Holding the Wheel While Cutting.= In the wheel-cutting engine as usually met with, the wheel (when not mounted on an axis) is held against the chuck by a hollow steel cone, on which presses an arm that slides on a vertical pillar and can be clamped in any position. The hole at the end of this arm does not always, therefore, correspond with the point of the cone, and, as a consequence, the wheel often gets displaced during cutting. This inconvenience can be avoided by adopting the following device, which we have seen in use with several watchmakers.

[Illustration: _Fig. 197._]

The pillar with its sliding arm is replaced by an iron or steel piece of the form G, Fig. 197. The point _a_ is received by the central hole at the lower end of the division-plate axis, while the screw _b_ presses on the point of the cone, clamping it firmly. Further explanation seems unnecessary; we would only add that the piece G must be made strong and perfectly rigid.

CUTTERS FOR FORMING THE TEETH OF BRASS WHEELS.

=407.= For making the teeth of the wheels of a train, a special form of cutter, set to revolve on an axis, is employed, and it may be constructed on either of three distinct systems.

[Illustration: _Fig. 198._]

[Illustration: _Fig. 199._]

(1) A single cutter mounted on an arbor, as at A, B, Figs. 198 and 199; this may be termed a _single cutter_.

(2) A circular cutter, formed of a series of such single cutters, which will be termed a _multiple blade_ or _composite cutter_. Two specimens are shown at F, J, Fig. 200.

[Illustration: _Fig. 200._]

(3) The pinion, or steel wheel cutter or mill, formed of a single piece of metal, as seen in Figs. 201, 202 and 203. These may be described as _mill_ or _file cutters_.

=408.= =To Make a Single Cutter.= The form shown at A, Fig. 198, is roughed out to as nearly as possible the required form in good steel. Some makers, possessed of exceptional skill, make them entirely by hand, and they make very beautiful teeth by this means; but as a rule watchmakers cannot look for such success, so that it is better to complete the formation of the cutter in a specially arranged tool.

[Illustration: _Fig. 201._]

[Illustration: _Fig. 202._]

The two sides may be made in the wheel-cutting engine, with the same mill cutter, which is inclined when used to undercut the acting edge; but this operation is not as easy as it appears at first sight, and the watchmaker will find it to his advantage to make the following device:

[Illustration: _Fig. 203._]

A spindle, _b d_, Fig. 204, supported between the runners, _t_, _v_, serves as an axis for the arm _f g h_, which is bent at _g_ so as to afford a support to a conical cutter _a_, driven on the ferrule _c_. The descent of this arm is limited by an adjustable stop, fixed to the bed of the turns.

Having removed the T-rest, replace it by the rod N, to which the cutter is clamped by a screw _k_, after being roughed out so as to reduce the work required of the cutter.

Place N so that the conical cutter occupies the position indicated at _z_, and, if a slight pressure be applied at _h_ while _a_ is caused to revolve, both the straight and curved portion of the side will be formed, and the side will, at the same time, be bevelled to an angle corresponding with that of the cone. The curved portion of the side will be more or less undercut, according as the arm _h_ is depressed below the horizontal plane passing through the axis of the lathe. The opposite side is formed by inverting the piece _f g h_.

[Illustration: _Fig. 204._]

In smoothing or polishing it is only requisite to replace the cutter by a smooth conical roller, and to work as before.

=409.= The cutter is sometimes fixed in the arbor as shown in Fig. 198. The arbor itself is thick and perforated with a round hole in which the tail of the cutter accurately fits, a slight pressure applied by the screw _m_ being sufficient to make it steady.

For cutting the escape-wheels of clocks the arbor should have a velocity of about 200 turns a second.

M. Peupin, a skilful watchmaker who adopts the practice here given, having observed that with a sharp cutting edge he did not obtain a sufficiently smooth surface, succeeded in obviating the difficulty by drawing a polisher with rouge along the cutting edge, maintaining it at right angles to the plane of the cutter. This operation, if carefully executed, will serve to remove the feather-edge, to make the edge even and yet not dull, and to secure a highly polished cut surface. The sides of the teeth will present a proportionately better surface, according as the portion _c a_ (M, Fig. 198,) approximates towards the dotted line _c d_.

His escape-wheel teeth are cut in successive stages. The last stroke of the cutter is given by advancing it against the side of the wheel, so that the cutter axis remains in the plane of the wheel.

=410.= =Triangular Cutters.= When a cylindrical or conical mill is not available for finishing and sloping the sides of a cutter, it may be replaced by a triangular cutter (T or C, Fig. 205,) and when the application of much force is required there may be a pointed bearing; but this is seldom necessary.

[Illustration: _Fig. 205._]

If carefully hardened and set, such a cutter gives a clean cut; of course it will not act for as long a period as the conical form above described, but this is of comparatively little importance, since the blank cutters are always roughed out previously to nearly the requisite shape.

=411.= =To Make Several Cutters at Once.= By adopting the following method, it is possible to make several such cutters in one operation.

Turn a steel disc of the form of an ordinary mill cutter, as shown at _l p_, Fig. 200. To finish it, giving the same curvature to the two sides, take a piece of steel, C, and shape the corner _r_ to exactly correspond with the side of the point or ogive of a tooth, bevelling it so as to give a cutting edge at the upper surface; then harden and smooth it with care. Having fixed it in position in the tool that carries the arbor _a_ and the roughed out disc (whether this be the lathe, wheel or pinion-cutting engine, or a special device) in the required position, one side of the disc may be finished. The arbor _a_ is then reversed and the other side finished in the same manner, so that both sides have the same curvature in opposite directions.

Of course the tool C may be advanced against _l p_, either sideways from _r_ towards _l_, or radially in the direction _l p_, as is most convenient. Or the tool might remain fixed and the disc advance against it radially or laterally.

The traverse slide in a lathe is usually provided with a stop; it would then be very easy to form one side of the disc in such a tool, afterwards reversing the arbor and forming the other side.

If a very good cutting edge is desired, the sides should be smoothed and, when the disc is completed, it may be divided into pieces similar to B, Fig. 199, each of which will serve as a cutter. It will be noticed that the acting edge is not undercut behind; it is thus necessary to slope the cutter a little as shown at B, as otherwise the rim will choke in the spaces of the wheel, straining it without cutting.

=412.= =Composite Cutter Formed of a Succession Of Single Cutters.= By mounting a series of identical single cutters round the circumference of a disc, a circular cutter can be formed in the manner indicated in Fig. 206. The upper portion represents the arrangement of the pieces while they are being turned, and the lower portion shows their positions when the cutter is ready to be used. M. A. Croutte, to whom we are indebted for several of the details here given, was much surprised that this form of cutter is not better known, since it possesses certain special advantages; we will summarize his remarks on the subject.

[Illustration: _Fig. 206._]

The separate cutters _b_, _g_, etc., Fig. 206, are not undercut from the acting edge backward; they are merely reversed, so that this

## acting edge is towards the front, in other words it lies along the

radius. These separate pieces possess a special advantage in that they can be used until the steel is quite worn out by the setting; in this respect differing from the undercut cutters, for they are not altered either in form or thickness by setting.

As a set-off against this important advantage, they are characterized by the inconvenience of requiring that the two sides of the blade be exactly in a plane at right angles to the axis, and that the slide carrying the cutter-arbor shall move in a direction parallel to this plane. And even when this double condition is satisfied, there will be friction of the two sides above the dotted line _i j_, Fig. 199, against the sides of the teeth; and if the above named conditions are not satisfied, the cutter, being presented edgeways, will be choked with brass, and the results will be unsatisfactory.

=413.= In order to ascertain whether such a fault exists, it is only necessary to notice whether the cutter becomes brass-colored on one side towards the point, and on the other more inwards, and the sides of the teeth exhibit striæ or scores in opposite directions, as indicated at E, Fig. 207. The white strip, 1, 1, corresponds to the bottom of a space between two teeth; 2, 2, and 3, 3, the two sides of this space, spread out like an open book.

[Illustration: _Fig. 207._]

By examining the marks with care, and noticing the direction in which they are inclined, it will be possible to ascertain both whether the separate cutters are out of place, and in which direction the arbor should be moved in order to correct any error.

We must, then, repeat that all the cutters must satisfy this condition, because if only one is wrong it will produce the scores here referred to.

The necessity of these precautions in the use of such a composite cutter, and the fact that the friction of the portion above the line _i j_, Fig. 199, renders it difficult to obtain a polished cut (which is essential for such delicate depths as those of watches), have doubtless prevented its use becoming general. For work that is somewhat larger or rough, it will be found to give satisfactory results and will last longer than a single cutter. A lubricant, such as glycerine or oil, should be applied to it.

=414.= =Composite Cutters with the Cutting Edges Undercut.= An old Paris clockmaker, Brisson, used a cutter of the form F, Fig. 200, for the teeth of his wheels. He undercut the two sides of the blades by means of a small special tool. Strictly speaking, the operation can be performed by hand.

In order to ensure that the curves that form the ogives of teeth are alike on the two sides of a cutter, he made a series of templates or standards of the form C, Fig. 206, in which were two holes, C and _c_, of equal diameter. The upper one, which might be funnel-shaped so as to give a cutting edge, was half cut away, and, after being hardened and set, could be used to give a final stroke to the circumference of two discs of equal diameter. These two discs, or one cut through a diameter would suffice, having been brought by a file to the form H, and joined as shown at _r s_, can be mounted eccentrically so as to present a cutting edge to the roughed out cutter A; the two sides can thus be made even. The disc may then be finished by cutting away the metal so as to give the form shown at F, Fig. 200.

By the aid of the standards he could easily reproduce the same forms of teeth when required.

Fig. 200 comprises, at J, a cutter for the teeth of watch wheels of the form employed successfully by M. A. Phillippe. The figure will explain itself.

We have known a Geneva wheel cutter who employed these composite cutters with advantage in making duplex wheels. The principal difficulty he experienced arose from the distortion of the metal in hardening, because the acting portion naturally lengthened a little. This form of composite cutter certainly demands careful workmanship, but, if the construction, hardening and polishing are good, it will produce fine work and will last a long time.

=415.= =General Observations on Cutting the Teeth of Brass Wheels with a Single or Compound Cutter.= High-class English watches, the movements for which are made at Prescot, in Lancashire, have the wheel teeth made by a composite cutter after the wheels are riveted to their pinions. We have remarked that these watches make less noise when running down than those in which the teeth have been formed with a mill or continuous

## action cutter.

Success in forming teeth with cutters depends mainly on the securing of a good form as regards the cutting edge, and on its being maintained in good condition; on the steadiness of the entire machine, so as to avoid vibration; on the weight of the wheel, and on the velocity of the cutter being sufficient. A cutter ought never to assume a brassy color except when it requires setting; if it does so, and this is not the case, it proves that the metal is being strained or scraped with friction. The velocity must be very considerable; greater with a single cutter than with one that is composite. The velocity is limited by that point at which the heat generated would cause the oil to evaporate, soften the cutter, distort, and sometimes even displace, the wheel operated on. The engagement of the cutter with the metal must be very slight, and should never be increased suddenly.

Attempts have been made to enclose the arbor bearings in horn, but it is liable to be distorted by the heat.

Before dividing the disc into cutters it is essential that the two edges be carefully smoothed, and this without their being distorted. This can easily be done in an old depthing tool, using an arrangement like that shown in Fig. 208. The lap must be of hard wood, and its right-hand corner rounded off so as to resemble the side of a tooth; it is set to engage with one side of the cutter. We say the right-hand corner, because a lateral pressure can then be applied. It is important that the surface as left by the graver be clean cut, because if the smoothing is too much prolonged, it will deform the cutter.

[Illustration: _Fig. 208._]

=416.= In some factories it is usual to use discs about 2½ inches in diameter, for cutting the teeth of brass wheels in timepieces. The single cutters are arranged round the circumference as follows: One forms a space between two teeth; the one immediately preceding forms the right-hand side of the ogive, and that which follows forms the left-hand side. By adopting such an arrangement of separate cutters, if their side that lies against the disc is slightly inclined backwards it is no longer necessary to bevel off the cutting edge.

MILL CUTTERS FOR STEEL.

=417.= =Pinions, Keyless Wheels, Etc.= The cutters that last for the longest period when used for cutting steel are those formed like a file; but a watchmaker is not always in a position to make them himself; we will, therefore, here only speak of those he can make, the description of the first few being taken from a work by M. A. Phillippe, of Geneva, _Les montres sans clefs_ (keyless watches).

=418.= =Cutter for Forming the Inclined Teeth of Winding Pinions.= Fig. 201 shows at S a section along the axis of such a cutter, and at P a side view. When it is believed to be of the required form, rest a piece of lead on the T-rest of the lathe and press it against the rotating disc. The impression made in the lead will afford a means of ascertaining both whether the form is correct, and whether the surfaces are smooth enough. This last point is important.

The cutting edges are formed by merely making a number of notches around the circumference with a tool for cutting ratchet teeth. Then advance this ratchet cutter so that it may engage with the convex edge of the cutter operated upon, and against the back of the teeth of this cutter; the ratchet cutter is then in a position to form a second face, _o i_, by which the teeth of the cutter are undercut at the back, but in such a manner that a small flat surface _o a_ is left in order to retain the form. When a cutter made in this way will no longer bite, it may be set by passing a hard slip of whetstone over the faces of the teeth.

The ratchet cutter employed for making this cutter should never be pressed against it heavily.

=419.= =Cutter for Ordinary Wheel Teeth.= We will now pass to the consideration of cutters for forming teeth of the usual shape, of intermediate steel wheels, set-hands wheels, pinions, etc. They may be made as follows:

The rim is indented with small fine ratchet teeth, _b d_, Fig. 202. Any burr produced on the sides is then carefully removed, and the cutter is placed in the wheel-cutting engine, and notches, _c_, _c′_, _c′′_, _c′′′_, etc., are formed on either side with a flat square-edged cutter of such a thickness that the circumference is about equally divided into hollows and prominences. It is important to note that the right side of the teeth must be but slightly roughed, not more than is required in order to raise a slight burr, all that is necessary to form the cutting edge of this portion of the disc. In roughing these sides, at least one out of every two of the small ratchet teeth on the circumference should be left untouched, so as to ensure the required thickness being maintained.

The cutter shown in section and elevation at S and P, Fig. 201, might be cut on the side _n_ in the manner here explained, and the convex portion _k_ might be indented with a fine ratchet-toothed cutter, carried in the hinged cutter-frame of the wheel-cutting engine. The degree of penetration may be determined by fixing an ivory disc against the cutter and concentric with it, the two differing in diameter by the depth the cuts are to be made. The teeth will be rather too square towards the circumference, but their form can be carefully corrected by hand. It is obvious that the very greatest caution is necessary in hardening cutters.

=420.= =Rose-Cutters or Forming Pinion Cutters.= As the edges of pinion cutters are rounded, they can be made in the manner suggested by Thevenin. Supporting the roughed out cutter in the cutter-frame of a wheel-cutting engine, he fitted in the axis of the division-plate a kind of rose-cutter, N, Fig. 205. Its extremity, _n_, instead of being flat, is hollowed out as indicated by the dotted line, and, by presenting the cutting edge thus obtained endwise to the grooved edge of the cutter, the correct form can be given to it. With a mushroom-headed piece of steel and oilstone dust, the cutting edge of the rose-cutter can be made more or less acute by modifying the angle of this steel lap.

=421.= =Other Forms of Pinion Cutter.= When a cutter is merely required for a special piece of work, and not for continuous use, it will often be sufficient to make it as shown at A, Fig. 203; this is made by grooving the disc (_c_), or forming its edges as at _d_, after which a series of teeth are cut on the periphery with a revolving cutter, taking care to leave no more burr on one side than on the other. Then pass a smooth worn file (or a worn flat cutter) over the faces of the teeth, applying oil at the same time, so as to produce a slight burr on the edges; if the file is not allowed to bite too much and is well managed, these minute ridges will be uniform. After hardening, the cutter is ready for use.

If the faces were smoothed without subsequently applying the file, the cutter would not bite; for its action depends on the slight projection of metal that corresponds to the file-cuts. The cutter is nothing more than a circular file, with two cuts per tooth. If the corners are turned over evenly by means of a very hard burnisher the same effect will be produced; but this operation is delicate, as the amount of metal turned over must be the same in every case.

When a cutter does not bite, it must be softened and restored to its initial condition.

=422.= Or the following method may be adopted when it is required to make a cutter for a special purpose.

Proceed at first in the manner just described, but the periphery is divided into a greater number of teeth with a flat cutter, and to a rather greater depth, as at E, Fig. 203. Bend backward each tooth to a distance equal to about half a space by any convenient method; for example, by a lever resting at the bottom of each space and pressing against the corner of the tooth, etc. Before bending the first tooth introduce a piece of brass into the space behind it, of a thickness equal to about half this space, so as to avoid bending too far; for succeeding teeth the thickness must be about equal to a space; thus E will become E′. An inspection of Fig. 203 will suffice to make the operation evident; it amounts to bending back a series of separate cutters. The disc is then hardened, and the faces of the teeth are smoothed when they do not cut well; or merely smooth those that are the first to become dull.

It is important to employ soft steel that has previously been well annealed.

=423.= =Cutter for Making Square Spaces.= The teeth of such a cutter can be easily formed with a file, as shown at L, Fig. 209, the edge of the cutter, _f_, being passed backwards and forwards in the direction of the arrows, applying considerable pressure and at the same time slowly rolling _f_ around. Or the cutter may be set up on a short arbor between the centers of the lathe; then pass the file backwards and forwards across the edge until the cuts are formed, slowly advancing the file in the meanwhile, so as to form the cuts around the circumference without once raising the file. The cutter must then, of course, be hardened.

[Illustration: _Fig. 209._]

=424.= =Forming Cutters with a Milling Tool.= The roughing of a round-edged, or even of a square cutter, can also be effected with the aid of a milling or “nurling” tool, proceeding in the same manner as when milling the heads of screws, etc. The tool must be in good condition, well provided with oil, and applied with considerable pressure against very soft steel.

If necessary, the workman can make the mill for himself; it is shown at M, Fig. 210. F shows the method of applying it to the cutter, and by

## partly turning the mill (of course carried in a strong holder) around

its point of contact with the cutter, as indicated by the dotted lines, the rim of F will be evenly roughed all around.

[Illustration: _Fig. 210._]

With good steel fairly satisfactory results are obtained in this manner, but it is needless to observe that such cutters never bite as well as those made in the usual manner.

=425.= =General Observations.= When cutters are used with steel they must be driven at a less velocity than when cutting brass, and, as M. A. Phillippe has observed, it is best to make the cutters for steel of small diameter (about half an inch). They are more easily made and are less distorted in the hardening. The velocity should diminish as the diameter increases; for too great a velocity, especially when the diameter is great, will dull the cutter and soften it, owing to the heat produced.

Cutters must be turned very true: it is advisable to give them a last stroke with the graver after they are fitted to the cutter-arbor that will subsequently carry them.

When operating on steel it is best that the cutter frame of the wheel-cutting engine be advanced by a screw so as to give it a slow and easy motion; the results obtained are more satisfactory than when it is advanced by hand or with a lever.

The following practice is not uncommon in factories when it is desired to reproduce the exact form of a cutter. A notch is made with the cutter in the edge of a piece of steel, X, Fig. 211, or a series of notches _o o′_, etc., can be made by several cutters in the circumference of a disc Z (same figure). After being hardened and sharpened at the cutting edge, this disc is fixed at the center of the division-plate of a wheel-cutting engine, and can then be used to complete the grooving of any cutter that is set in position on the cutter-arbor before hardening. The positions opposite to which the notches were cut should be marked on the chuck, so that they may always be set-square to the cutter.

[Illustration: _Fig. 211._]

=426.= Besides the forms of cutter above described for operating on steel, we may mention that circular cutters may be used in which all the notches around the circumference have been polished, thus removing the burr, and preventing them from acting in the manner of a file. But while, with the former kind, a somewhat rapid rotation is necessary (although not so rapid as when cutting brass), with this latter class the movement must be comparatively slow, and produced by means of a hand-wheel; otherwise they will not cut, since the action depends rather on the application of pressure, and resembles that of a slide-rest cutter. The distance apart and width of the teeth of the cutter, as well as their inclination, are of importance; if too far apart they occasion a waste of time; if too large the machine will act in a jerky manner, and when too narrow, an excessive pressure will be needed in order to make the cutter bite the steel, which, it is to be observed, must always be thoroughly annealed. The edge must be well supplied with oil or soapy water when in action.

It is generally found best to advance the cutter against the edge of the steel rather than across it.

TOOL FOR MAKING CUTTERS.

[Illustration: _Fig. 212._]

=427.= The instruments usually employed for making cutters for the teeth of wheels and pinions are complicated and expensive, but the author has designed one for his own use that is comparatively simple, and can be made by any watchmaker. When the reader has grasped the principle on which it acts he will be able, without difficulty, to modify it so as to suit his requirements.

[Illustration: _Fig. 213._]

The frame B B _b_, Figs. 212 and 213, consists of the body of the tool, B B, and a bar _b b_, which is attached to it by screws. Between the two the division-plate P rotates on an axis E R. The end E of this axis is formed as a chuck to receive the cutter _f_, which is clamped by a screw _t_.

The support S _s_ J is held with friction in the lower part of this frame, to carry the cutter-holder A L M. This cutter-holder is hinged at _n_, so that it can receive a double motion, revolving about a horizontal axis J, and about an inclined axis _n_.

The portion A L of the cutter-holder carries a perforated arbor _a c_, with a ferrule _c_ that receives the tail of the small rose-cutter, which will presently be described.

The end M rests against a guide G, held by a vane _o z_, which is pivoted on a pillar _z_, and can be clamped in either of the directions _z y_, _z x_, or by one of the screws _o_, _o_.

=428.= We will now consider the mode of action of the machine. Having set the little arbor _c a_ in rotation, rest the end M of the arm against the guide, and gradually advance the rose-cutter towards _f_; the edge of _d_ will form the first notch in the grooved rim of the cutter, and then will be raised from contact with it, owing to the influence of the guide G. After moving the tool-holder back to its initial position, advance the wheel P by a tooth, repeat the operation, and so on.

=429.= If the cutter _f_ has to be notched on both sides, it must be reversed on the chuck; turn the guide so as to point in the direction _z x_, corresponding exactly to _z y_; then having set the cutter-holder in the line _z h_, recommence operations. The two grooves of the cutter will then necessarily be of similar form.

Teeth can be cut on the rim of _f_ by using a cutter of the form F, Fig. 214, and holding M against a straight vertical guide.

With a given divided wheel, P, the teeth can be brought nearer together by reducing the diameter of the cutter, and _vice versa_. It is well to have some change wheels, but a better plan is to advance the division plate by the aid of a tangent screw.

[Illustration: _Fig. 214._]

=430.= =To Make the Several Accessories.= _Form of the rose or star-cutter._ The rose-cutter is formed of a mushroom-headed piece of steel. Such a conical cutter is shown at C and R, Fig. 215, and at F, Fig. 214. F and C are cut in the same way that conical cutters are always made, and R is a small triangular prism that only cuts by its three corners, _a_, _a_, _a_. As it is necessarily very small when employed in making the cutters for watch pinions, it must, in such a case, be supported at the neck by a little fork. Moreover, it must be brought gradually against the steel to be operated upon, so as only to engage a very little at a time. With a view to this, it is advisable that the cutter-holder be advanced by a screw.

[Illustration: _Fig. 215._]

The star-cutter, shown at E, Fig. 216, is at times substituted for the rose-cutter. It cuts with the corners _e_, _e_, etc., whether it be going to the right or left indifferently. Or a triangular cutter like T, Fig. 216, can be used in its place; but its angles are fewer and less acute, so that they become dull more rapidly.

A few trials will be needed in order to determine the most convenient rate of movement of the several parts; and the edge of the cutter _f_ must always be liberally supplied with oil. A little can may be so arranged as to allow oil to fall drop by drop on to the cutter _d_, Fig. 213.

[Illustration: _Fig. 216._]

=431.= _To make the guide._ Having mounted a plate, G, on the vane _o z_, trace out the approximate form of the cutter with the point of M; then cut off the superfluous metal, leaving a slight margin. This excess is necessary because the curvature of the guide is not the same as that of the cutter, for the indentations as they spread out from the center (_t_) become gradually deeper. The guide should be tested from time to time by operating on a blank brass disc fixed in place of the cutter _f_ and the guide must be modified as experience shows to be requisite. Its edge must be saddle-shaped so that the middle may correspond exactly with the two dotted lines _z x_, _z y_, Fig. 213.

The position of the disc on the chuck _t_ must be brought to correspond with the guide by carefully turned washers placed behind it.

=432.= _Driving attachment._ Fig. 217 shows one system that may be adopted for connecting the ferrule C with a driving wheel. All that is required is that the instrument be set in such a position that this ferrule is placed as indicated in the figure with reference to the distributor.

[Illustration: _Fig. 217._]

=433.= _Cutters of uneven thickness at the circumference._ It is well-known that the edges of the cutters of rounding-up tools (=435=) are made to taper off around the periphery. In order to indent such a cutter, the guide must be mounted on a slide, so that it may be gradually displaced while the operation is in progress, by an amount previously determined upon.

The desired result can be obtained with sufficient accuracy by moving the guide backwards by successive stages with a screw. The end _k_ of the arm M, Fig. 213, is slightly tapered, so that a gradual depression of M occurs, and each cut is deeper than that which preceded it.

[Illustration: _Fig. 218._]

=434.= _Modification in the construction._ This instrument may be modified as follows: The disc to be operated upon is fitted to the chuck of the division-plate D, Fig. 218, which is vertical, and the entire system is capable of a movement of rotation round the axis of the base P. Having set the disc in the plane _a b_, as shown in the figure, clamp P; then, by traversing the cutter-holder, the teeth on the side of the cutter towards _a b_ are made. This cutter frame having now been removed, the base P is turned until the cutter is in the plane _c n_, such that it is equally inclined on the opposite side of the axis of the cutter frame; the teeth on that side may then be made, the star-cutter being rotated in an opposite direction.

It is unnecessary to prolong our explanations of the instrument, as the details already given will suffice for any intelligent workman.

TOOLS FOR CORRECTING THE FORM OF TEETH.

=435.= =Rounding-up Tools.= In Europe it is the practice, in making watch wheels, to first notch the circumference by means of a flat circular cutter in a wheel cutting engine, thus forming a number of square teeth. They are subsequently rounded off to the usual form, after the wheels are riveted to their pinions, in a special tool.

The apparatus employed for this purpose is termed a rounding up tool, and its principal feature is a mill cutter F, Fig. 219, the portion _a b_ of whose circumference is cut away and replaced by a guide _g f_ made of steel spring, and so fixed as to coincide with the edge of the cutter at _f_, and incline at _g_ in order to compel the cutter to pass, at each rotation, into consecutive spaces of the wheel. Two screws are provided, the one _f_ for setting the guide opposite the edge of the cutter, and _g_ for placing the free end of the guide opposite to a space.

This tool acts with great rapidity, a fact which has led to its being very extensively used in the factories of France and Switzerland, although the ordinary system of wheel cutting is preferred in England for all the better class of work. For it should be noted that the rounding up tool does not correct any errors that are due to bad dividing; for example, if a wheel is found to have some of its teeth larger than others, the tool can not be relied upon to correct them; on the other hand, if a wheel is exactly divided it is improbable that the employment of this tool will occasion irregularity.

[Illustration: _Fig. 219._]

The instrument we are discussing is, however, not much used by watch repairers, although they are frequently called upon to touch up the teeth of wheels, or to slightly reduce the diameters of their pitch circles, operations which cannot be done by hand with much chance of success. The limited use to which rounding-up tools have been put is owing, in great part, to their high price, but cheaper tools on this principle are now coming into use.

=436.= One of these is shown in Fig. 220. The wheel to be operated upon is held against a small table at D between two vertical runners with guard-pivot centers, and a cutter of the form shown at Fig. 219, is fixed at C to a suitable chuck of a small lathe-head B; this is caused to revolve by the hand-wheel A, a supplementary pulley K taking all strain off the axis. The three milled-headed nuts seen at E, F, and G are for adjusting the instrument; E for moving the lathe-head, so that the cutter is in the same plane as the axis of the runners, a position which is determined by the pointer I; F for advancing the wheel against this cutter; and G for setting the plane of the wheel to pass through the axis of the lathe-head as indicated by the index H. The instrument is accompanied by a number of cutters to suit the various sizes of teeth ordinarily met with, as well as of tables to support wheels of different dimensions.

[Illustration: _Fig. 220._]

=437.= =Ingold Fraise or Cutter.= =Rounding-up Cones.= Either the cutters devised by M. Ingold, or the rounding-up cones of M. Berlioz, may be used for correcting the form of wheel teeth.

The Ingold fraise is a small steel cylinder perforated through the axis so as to be mounted on an arbor, and having a number of longitudinal notches on its circumference which makes it resemble a pinion, the points of whose leaves have been ground off. The spaces of the fraise are of the exact form required to be given to the teeth of the wheel, and their surfaces are covered with fine file cuts so as to enable them to remove metal from the wheel operated on.

Having mounted the arbor that carries it between two centers of a depthing tool (made especially strong for the purpose), the wheel is supported by its axis between the second pair of centers (with guard-pivot points). If now the fraise be advanced by the screw until its teeth engage with those of the wheel, and either be caused to rotate, it will drive the other, and the fraise will thus shape the teeth to a pre-determined form, the faces of each notch acting the part of a minute file introduced between the teeth.

It will be observed that such an instrument is preferable to the ordinary rounding-up tool, in that it may be relied upon to bring all the teeth to the same shape, but, on the other hand, the latter tool has an advantage in being available for slightly reducing the diameter of a wheel when a depth is found to be too strong.

=438.= An objection has been urged against the Ingold fraises on the ground of expense, as each dimension of tooth evidently requires a cylinder specially adapted to it. This fact has led to the introduction of “rounding-up cones” the invention of M. Berlioz, which act on precisely the same principle, but are conical instead of cylindrical, so that each fraise evidently takes the place of a number of Ingold fraises. The total number being proportionately reduced. But great dexterity is required in their use, so that they cannot be successfully employed until after numerous trials.

=439.= =Exact Rounding-up Tool.= The author has devised an instrument for giving to the teeth of wheels the exact form determined upon by theory, but as it is of too elaborate a nature to come into general use, we shall not do more than here refer to it. It is rather of a nature to be used for scientific work, but might be found of considerable value for accurately forming the blades of cutters that are used in grooving the circular cutters employed for cutting the teeth of wheels.

=440.= =To Round Up Teeth By Hand.= We have seen a country watchmaker proceed somewhat as follows: His method was only effective, however, for ensuring the verticality of the file, and did not maintain it straight, nor could the curvature of all the teeth be relied upon to be the same; these two conditions are satisfied by the system here explained.

Formerly watchmakers possessed very considerable skill in this kind of work, as the teeth were always formed by hand; but at the present day, for want of practice, there is not one to be found in a hundred competent to round up a wheel properly by hand alone. Recourse may be had to the following expedient in an emergency; it necessitates the construction of a small special tool, but this is so simple that it can be made in a few hours by an apprentice.

=441.= Take a bar of metal or hard wood, made smooth on its faces and square at the corners (R, Fig. 221), and adapt to it a slide, _c c_, through the center of which a slot is cut to receive a clamping screw; it slides between the four pins indicated in the figure. An arbor _a_ is supported by _c c_, parallel to R, having a plate at its end on which a wheel to be operated on can be fixed by three screws and a loose plate. It is centered by the circumference before clamping these screws, rotating _a_ with a bow, and it may be well to place a piece of tissue paper under and over the wheel in order to avoid scratches. V is a tongue that can be introduced into the space between two teeth in order to prevent the wheel from moving.

[Illustration: _Fig. 221._]

Two arms, _p p_, screwed to the bar R R, support the handle of the rounding-up file _l_, which consists of a large cylinder _t_, _t_, that slides in the arms _p_, _p_. The cylinder T must be exactly parallel to the arbor _a_, and the longer it is the better. The file-holder _s_, also shown detached at Y, Fig. 222, is merely driven onto the rod _t_. The distance between the center of the axis _t_ and the face of the file (_b b′_, Fig. 222) is equal to the radius of the circle that embraces the external curves of two or more teeth, as will be explained.

[Illustration: _Fig. 222._]

The several parts being arranged as shown in Fig. 221, and the bar clamped in a vise at E, it will be obvious that, if the wheel is held in two fingers of the left-hand so as to prevent it from being displaced, while the rod T is moved up and down, at the same time rotating it with the right-hand, the curves of two teeth will be adjusted to correspond with the arc _o o o_ (Z, Fig. 223), and, by transferring the tongue V to the next succeeding space, the curve _i i i_ can be struck.

[Illustration: _Fig. 223._]

=442.= _Observations._ The curvature of the point of a tooth coincides very closely with a circular arc described from a certain definite center, and comprising either two or three teeth. In order to realize these conditions in practice, the slide _c c_ is so adjusted that the axis of T passes just within the circle that passes through _o_, _o_, _o_, etc. (Z, Fig. 223), at which the points of the teeth commence; by making trials with two or three file-holders that differ in regard to the distance _b b′_ (Y, Fig. 223), it will be easy to select the most suitable for producing the required curve. After operating on all the teeth in succession, advance the wheel by means of the screw D, and again work around the circumference, and so on. The progress of the work should be frequently examined with the glass.

It is possible to dispense with the tongue V, and to merely steady the wheel by hand; the work is thus done more rapidly, but must be examined with very great care.

We would insist that the lengths of the two axes are an element of success. In operating on watch wheels T should not be less than six inches long.

By suppressing the tongue the motion of the two axes may be co-ordinated so as to form any theoretical curve; This is the case in the exact rounding-up tool already referred to, but it of course renders the instrument more complicated.

=443.= =To Ease a Train of Wheels.= In very many of the cheaper watches and timepieces now met with in commerce the teeth are rough and badly cut, and the pinions but little polished, so that watchmakers are constantly complaining of the difficulty of securing even a moderately good depth. In such cases they have a simple method to adopt in addition to those already referred to, namely, to polish the teeth with a piece of charcoal.

A piece of smooth, even charcoal, with regular fibre, is moistened with oil or water, and passed across the teeth individually; first with the fibres lying in the direction of motion, and afterwards with them at right angles to that direction.

If the charcoal is carefully selected and lightly applied for a sufficient length of time and no more, the ogives will be found to be nicely smoothed, and the depth will run far more easily than it did previously. It is dangerous to use quick-cutting charcoal, as it is apt to deform the teeth.

Smoothing with a brush charged with charcoal powder cannot be regarded as anything more than cleaning; if the action is too much prolonged the form of the teeth will be spoilt.

TO TEST THE ACCURACY OF CERTAIN TOOLS.

=444.= =Drilling Tool.= First center the runner in the lathe, and ascertain that it is straight, cylindrical, and exactly centered; then fit a ring to it so as to slide with friction to (temporarily) limit the descent of this runner in the vertical stock of the tool.

After placing it in position, adapt to its lower end a collar, provided with a long index of soft brass, which is bent so as almost to touch the plate at its circumference. Rotate the runner and it will be shown to be perpendicular to the plate if the point of the index remains at the same distance from the plate.

As a confirmatory test the runner may be drawn up in the stock, and the trial repeated after bending the index nearly to touch the plate.

=445.= =Uprighting Tool.= If the two stocks or tubes that receive the runners are exactly in line, a runner should move easily through the two at once.

Setting the points in contact in various positions in a vertical line, observe whether they coincide, both when at rest and when rotated together or independently.

First ascertain that the table is at right angles to the axis in the manner already explained for the drilling tool, making the necessary tests with the two runners independently. Then support between their points a short arbor carrying a soft brass index. The position of the lower runner being maintained constant by means of a collar as above explained, rotate the upper one by hand; its friction will carry the index and arbor around, the point of this latter being set close to the plate. Repeat the operation by raising the pair of runners and bending the index down to the same amount.

If in these various positions the point remains at the same distance from the table, it affords evidence that the tool is accurate.

An uprighting tool consists of two parts: the table carrying the lower stock, and the bridge that forms the upper stock. The base of this latter is a ring turned flat and co-axial with the stock, and is fitted accurately into a square groove surrounding the table, where it is fixed by screws.

Any watchmaker understanding this mode of construction will easily perceive when he has tested the tool in the manner above indicated, both what are its faults and how far he can correct them.

=446.= The English uprighting and drilling tools, and some of foreign construction, are combined on the same stand, and a good arrangement, made by Boley, is shown in Fig. 224. It will be seen that the drill can be set in motion by a hand or foot-wheel; the table is fixed in a vise and provided with two dogs for clamping the object. The drilling spindle is perforated throughout its length so that the drill can be held by an American split chuck.

[Illustration: _Fig. 224._]

=447.= =Depthing Tool.= As the value of a depth depends essentially on the overlapping of the teeth being the exact amount required by theory, it is specially important that the tool used for determining the distance between the centers of the wheels and pinions should be of the utmost attainable accuracy.

First ascertain that the spindle which serves as an axis for the two halves of the tool does not change position when they have been several times separated and brought together. For, if this were to happen, and a runner were uneven or the hinge not smoothed within, the parallelism of the two pairs of runners would be impaired.

The runners must be of equal thickness throughout, and should pass with ease from one head to that opposite. Their points and center holes must be seen to be in good condition, and, on placing them in their turns, they must be found to be both true and cylindrical. Having restored them to their places with the points together, move the pair lengthwise from one head to the other, examining the points in successive positions to ascertain that they coincide accurately, both when the runners are loose and when clamped. When the adjustment has been carelessly done the runners will be found to bend under pressure, causing the points to be displaced.

Having set two runners side by side and level, describe with them circular arcs on a smooth piece of brass from centers previously marked, first with the points just projecting from the heads and then projecting more and more. These tests may be made both within and without the tool; so that there will be four sets of tests in all.

It is very important in making the last-named trials, that the tool be maintained at right angles to the plate on which the circular arcs are traced; this condition can easily be satisfied by a special device, or by merely causing the compass to slide along a set-square. It may be added that the series of arcs should be drawn end to end, in order that it may be easier to observe their agreement or difference when examining with the glass.

=448.= When this series of tests has been gone through, and the points have been examined so as to make sure that there is no burr which bends over while tracing the arcs, it is possible to determine the value of the tool; we know whether it is perfect or not, and what corrections are required. As a rule there are two points mainly at fault; the holes in the heads are not exactly continuations the one of the other, so that they need to be broached out afresh and new runners have to be made. A careful and intelligent workman who is provided with suitable tools will be able, from the information given in this work, to correct, or at least improve, a defective depthing tool; but, as a rule, it will be better done by the maker.

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