Part 31

_Fig._ 6. is the Iron Setting-screw, which passes thro’ the Hole in the Fore-end of the Mortise, _Fig._ 2. and passes up to the Middle of the Spring by the prick’d Line _p q_ in the same Figure. The Use of this Setting-screw is, to increase or diminish the Proportion of Seed to be turned out by the Notches; and this it does by forcing up the Spring and Tongue (where there is one) nearer to, or farther from the Spindle, whereby the Seed-passage is made wider or narrower, as is shewn by the Three prick’d Lines in _Fig._ 2. and _Fig._ 3.

Observe, that the prick’d Line _p q_, _Fig._ 2. (being the Mortise of the Turnep-box) stands higher than the same Line doth in _Fig._ 3. which is the Mortise of the Wheat-box. The Reason of this Difference is, because the Spring in the Wheat-box bears at its lower End against the Tongue below the Seed-passage, and at its upper End below the Axis of the Tongue, whereby the Middle of that Spring is lower than the Spring of the Turnep-box, which, being both Spring and Tongue, bears against its Axis above, and against the Seed-passage below; therefore its Middle is higher. This Setting-screw should be placed perpendicular to the Tongue when at its mean or middle Distance from the Spindle, which may be supposed to be the middlemost of the Three mention’d prick’d Lines. This Setting-screw ought to be smooth and round at its End, which bears against the Spring; for, if it should have sharp Corners or Edges, the Spring might be wounded by them, and in time might break there, being press’d by every Notch that turns against it; and, as I have computed it, a Spring undergoes One hundred thousand of these Pressures in one Day’s Work; and yet, in my whole Practice, I have had only one Spring broken, and that was in drilling a large Sort of Peas with a Wheat-drill, and was occasioned by a jagged End of the Setting-screw, which was not placed perpendicular to the Spring, by which means the rough End of the Screw made Scratches against it a Quarter of an Inch long, and so deep, that the Spring broke off there: Let not this Setting-screw be any longer than just to force the Tongue up to the Spindle; for, if it should be longer, an ignorant Driller might happen, by the Force of the Screw, to break the Tongue, or its Axis; but in the Turnep-drill, which has only a Spring instead of a Tongue, the Setting-screw may be a Thread or Two longer; because the Spring will yield a little to it, after it touches the Spindle, and is sometimes of Use in that respect, when the Notches are too large. This Screw must be of such a Bigness, that it may not be in Danger of bending; for if it should be bent, it could not be screw’d up with any Certainty, because its End, being crooked, would be below its Place at one Half-turn, and above it at the other Half-turn, and so the Spring might be set farther from the Spindle instead of nearer, and nearer instead of farther, by the Crookedness of the Setting-screw. Its Head may be made with a Notch in it, to be screw’d in with a Knife, or else with a Head like a T, to be turn’d with the Fingers, which I think is best, especially for a Wheat-drill; because as the Brine and Lime, which stick on the Wheat, grow drier, it will run faster; and therefore the Setting-screw must be frequently screw’d in to lessen the Seed-passage.

The Seed-passage, or Place of Pressure, is where the Seed passes down betwixt the Spindle and the Tongue; and is in that Part where they are nearest together; for there the Seed is press’d hardest by the Force of the Notches, which carry it down: And this Passage is higher or lower, as the Tongue stands nearer or farther from the Spindle; for as it stands wider, it becomes nearer to perpendicular to the Top of the Mortise, and then the Seed-passage is higher; and when it stands nearest to the Spindle, then the Seed-passage is lowest. This appears in _Fig._ 3. by the Three prick’d Lines _a n_, _a o_, and _a p_.

The Spindle, with its Notches, is best shewn where it is large, and made of Wood, as that of the Wheat Seed-box; it is a solid Cylinder that passes thro’, and fills the great Hole, or hollow Cylinder, of the Seed-box; it is of various Lengths, according to the Distance its Wheels go asunder; it is always in large Boxes the Axis of Two Wheels, and turns round with them, as the Axis of the One Wheel of a Wheelbarrow does with that: These Wheels, by their Circumferences, measure out the Ground over which they carry the Seed-box, and, by the Notches in their Axis, deliver down the Seed equally, whether they move swift or slow; because an equal Number of Notchfuls of Seed will be deliver’d thro’ the Seed-passage at each Revolution of the Wheels.

The Notches resemble those in the Hinder-Cylinder of a Cyder-mill, which break the Apples by turning against the Notches of the Fore-cylinder, as our Notches turn against the Tongue; and bruise the Apples which come betwixt them, as our Notches might sometimes bruise soft Seeds, if the Tongue stood close to the Notches, without any Spring behind it to give Way to their Pressure, and return the Tongue again to its Place, at every Interval betwixt Notch and Notch.

The best Way, that I can think of, to shew the making of these Notches, is by a Section of the Spindle at right Angles, in the Middle of the Notches, as in _Fig._ 4. of _Plate_ 3. which is a Circle whose Circumference is cut off by Six Notches; which shew the different Sort of Notches, that increase or diminish the Proportion of Seed to be carried thro’ the Seed-passage by them: The Length of the Notches we never alter; but make them always parallel to the Axis of the Spindle, and of the Length of the Distance there is between the lower Ends of the opposite _Axes transversi_ of the Ellipses, or great Holes, of the Mortise; for if any Part of the Surface of the Spindle should be betwixt the End of a Notch and the Hole, one or more Seeds coming betwixt that Surface and the Tongue, might hold it open, and prevent its pressing against the Notch, to hold the Seed therein from falling without the Turning of the Wheels.

This Proportion of Seed is alter’d by the Number of Notches, and by their Depth or Breadth, or by both. _b c_ is the Depth of a Notch, which we call its Side; and is that which takes hold of the Seed, and carries it down thro’ the Seed-passage. The Manner of cutting this is seen by its being a Portion of the _Radius_ A _c_. The Bottom of a Notch is made in different Forms[264]: As, first, it may be convex, as is shewn by the curve Line _b d_. We may enlarge the Capacity of this Notch, by taking off the Convexity of its Bottom, as in the Bottom of the Notch shewn by the Line _e f_; and if we would increase it more, we make it concave, as _g h_.

[264] The convex Form is best for turning out a great Proportion of Seed; because such a Bottom may be broader than one of any other Form, in a Notch of the same Depth and Capacity; and such a Notch, having its Capacity more in Breadth than Depth, will be less liable to let fall any Seed without the Turning of the Wheels, than a Notch that is deeper and narrower, except it be very narrow, which it cannot be for throwing out a large Proportion of Seed; for a great Number of Notches cannot have altogether the same Capacity as a lesser Number of the same Depth may. The concave Notch, if it were as broad as the convex may be, would make the Interstice, that is before it, liable to be broken out, and so Two Notches would become One; but the Convexity of the other supports the Interstice like an Arch, and for that Reason may be made to reach almost quite to the Notch that is before it, without that Danger.

But of whatever Sort or Dimensions one Notch is made, all the rest should be the same exactly; and consequently, the Interstices (or Intervals) between Notch and Notch, of which the Line _f c_, being an Arch of the Circle, is the Breadth, must be equal[265], and cannot be otherwise, if the Notches are all equal and equidistant, as they appear in the adjoining _Fig._ 5. which is a Section like the former, and shews Six Intervals, with their Six Notches, of the Size wherewith we drill St. Foin with high Wheels; but when we would drill very thin, it is better to have but Four or Five Notches instead of Six.

[265] But these cannot be equal, unless the Notches are all of equal Breadth, and equidistant from one another; and if they are otherwise, the Seed will not be equally delivered to the Ground.

_Fig._ 6. shews a Notch of the Spindle. _a b_ is the upper Edge of the Side of the Notch, being always an acute solid Angle. _c d_ is the Edge of its Bottom, being always an obtuse Angle. _e f_ is the Angle made by the Side and Bottom, and is always shorter than the aforesaid Two Edges, by reason of the Obliquity of the Two Ends; this Angle is never obtuse, except when the Bottom of the Notch is concave. These Three Lines must be parallel to the Axis of the Spindle.

_Fig._ 7. is one End of the afore-described Notch; the Line _a b_ being joined to the Line _f d_ of _Fig._ 6. and the Line _a c_, being joined to the Line _b f_ in _Fig._ 6. would be the End of that Notch in its proper Posture; and then the Line _b c_, being an Arch of the cylindrical Spindle, would be the Edge of the upper End of the Notch. _a b c_, being the Area of this End, is a Plane, and, when in its Place, makes an Angle of Forty-five Degrees with the Axis of the Spindle. The other End is the same with this in all respects, except that, being opposite to it, it is inclined to it in an Angle of Ninety Degrees, at the bottom Angle of the Notch, at the Line _e f_ in _Fig._ 6.

_Fig._ 8. is a Notch lying with its Ends near it, and is of the same Dimensions with those appearing in the Seed-box, _Fig._ 3.

The Cover B appears with its upper Surface rightly placed in the Mortise, in _Fig._ 3. of _Plate_ 3. where its Breadth is shewn to be the same with that of the Mortise; but its Shape, and other Dimensions, are best seen in _Fig._ 3. of _Plate_ 2. where _s t_ is its Length, and reaches from the Hinder-end of the Mortise, to within the Tenth of an Inch of the upper End of the _Axis transversus_ of the Ellipsis; its greatest Depth is from _v_ to _w_, and is made so deep, that its Bottom, at _w_, bearing against the End of the Mortise, may prevent its Point, which is at _t_, from sinking down to touch the Spindle, which it neither must do, nor be so high above it as to suffer a Seed to pass between the Spindle and it, tho’ the Seed is not apt to pass that Way, because the Notches throw it forwards from the Cover. _z_ is the Hole, thro’ which an Iron Screw-pin passes, and screws into the opposite Sides of the Mortise, to hold it firm in its Place: ’Tis made so thin betwixt _x_ and _y_ both for Lightness, and that the Seed may come the more freely to the Notches, without Danger of Arching at that End. The Use of the _Cover_ is to prevent any Seed from falling down behind the Spindle.

_Fig._ 10. _Plate_ 2. is the Fore-end of a Wheat Mortise, with its Hole A, thro’ which the Setting-screw is screw’d, and passes up to the Back of the Tongue by the Line _q r_ in _Fig._ 3.

_Fig._ 9. in _Plate_ 3. is the hinder End of a Wheat Mortise, which by its prick’d Lines, and the Two right-angled Triangles they make, shews the Bevel of the Mortise, and also its Depth; it also shews the Difference of the Bevel of the Mortise, and that of the Tongue, _Fig._ 1. which is placed against it: These Figures having been already demonstrated in the Description of the Turnep Mortise, and in these, I need say no more of it, but that I think these last-mention’d Figures sufficient Directions for understanding and making the Mortise of a Wheat-drill.

_Fig._ 3. of _Plate_ 3. exhibits to View a Wheat Seed-box, with its Appurtenances, standing upon its Bottom; B the Brass Cover; C the Tongue hanging upon its Axis; _c_ the End of the Iron Screw that holds on the Spring, coming thro’ the Tongue, and filed smooth with it; _a_, _a_, _a_, are Three Notches of the Spindle, with their bevel Ends; _b_, _b_, are Two Interstices betwixt the Notches.

Hitherto we have been speaking of the Parts contained in the Wheat Seed-box; let us now come to the Parts containing: As, first, _d e f g_ is the upper Surface of the Brass Seed-box, shewing the Top of the Mortise, and what it contains; _h h h_, and _h h h_, shew the Ends of the hollow Cylinder, and its Bases coming out on each Side, farther than the Box; for if it did not project farther out than the Sides of the Box, the Surface of it would be so narrow, that it would cut the wooden Spindle by the Friction made between it and the Spindle; but the Surface, being of this Breadth, never wears into the Spindle, but makes it smooth and shining; _i i i_, and _i i i_, shew a Portion of the wooden Spindle (of an Inch and an half Diameter) coming out of the hollow Cylinder, on each Side of the Brass Box.

The Spindle is kept from moving end-ways, by Wreaths, in the same manner as the Axis of a Wheelbarrow is; which Wreaths shall be described together with the Hopper. _k_ is the Hole by which the Fore-end of the Seed-box is held up to the Bottom of the Hopper, by a Screw and Nut. _l_ is the Hole where the Hinder-end of the Box is held up, in the same manner as the Fore-end is. _m n o p_ shew where the Two Halves of the Seed-box are joined together.

_Fig._ 10. shews the Outside of One Half of the Brass Seed-box. A A A shew the Thickness of the projecting Base of the hollow Cylinder, which is made the thicker, to the end that the Hole may be bored large, and made an Inch and Three Quarters Diameter, when a Spindle that is to go therein is required to be of that Bigness, by reason of its extraordinary Length, as it is in the Fore-hopper of the Wheat-drill. B C shews the Thickness of the Ends of the Seed-box, whereby it is held up to the Bottom of the Hopper; if they are not quite a quarter of an Inch thick, they will be strong enough; especially C, which is the hindermost, and which is never pull’d down by the Turning of the Spindle, but is rather raised up by it.

D is the Head of the Counter-screw, to be turn’d by the Fingers, to press against the Side of the Setting-screw, to keep it from turning of itself, when it is worn loose.

E is the Hole for the Axis of the Tongue. F is the Hole of an Iron Screw-pin, which both holds the Cover to its Place, and also the Two Halves of the Box together. G is the Hole for another Screw-pin, which holds the Two Sides of the Box together. H and I are Holes for Two other Screw-pins, which likewise hold the Two Halves of the Box together, and are placed one above, and the other below, the Setting-screw; for otherwise that Screw, and its Counter-screw, might force open the Joining of the Box, and then the Setting-screw might be loose, and the Bevel of the Box might be altered; but these Screws, being one on each Side of it, prevent this Inconvenience.

_Fig._ 8. in _Plate_ 2. is one Half of a Brass Turnep Seed-box, lying with its Inside uppermost, which shews the left Side of the Mortise, and half the Fore-end, and half the Hinder-end, of the Mortise, and half of each Screw-pin Hole, by which it is held up to the Bottom of the Hopper. A is half the Hole of the Setting-screw, shewing in the Middle of it the End of the Counter-screw. B is half the Hole, by which the Steel Spring-cover is held in with a Screw. All the other Holes are for the same Purposes, as have been shewn in the Wheat Seed-box.

_Fig._ 9. is the whole Turnep Seed-box, standing upon its Bottom; Part of its Steel Spring-tongue appears in its Place, as also some of the Notches of the Spindle; but more especially the Cover A, which differs from the Cover of the Wheat Mortise, this being a very thin Spring, whose lower End just reaches to touch (but not to bear upon) the Spindle at the upper End of the transverse _Axes_ of the Ellipses; the Mortise being filed away at the End, in order that the upper End of this Spring, and the Screw which holds it, may not lie above the upper Surface of the Box. This Spring is made very weak, to the end that, if by any Chance a soft Seed should stick in a Notch, and be turned round, this Spring might suffer it to pass by without breaking it. B, C, are the Two Flanks or Sides, made necessarily of this Breadth, for bearing against the Wood of the Bottom of the Hopper, to prevent the Seed from falling out betwixt the Wood and the Brass, and that the Hole in the Hopper may be broader than this narrow Mortise of the Seed-box. The left Flank B, being next the wide Side of the Hopper, lies all open, except on the outside of the pricked Lines, where it is covered by the Wood of the End of the Hopper, when it is screwed on to its Place; but the Flanch C, on the right Side, will be all covered by the End of the Box, that will stand upon it, and will reach to the pricked Line that touches the Edge of the Mortise. D is the End of the Setting-screw, appearing in its Place with a Notch, whereby it is to be turned by a Knife; but I think it better to have an End like a T, to be turned with the Fingers. E is one End of the hollow Cylinder, which projects beyond the Flanch, that there may be more Room for the Crank to turn (without striking against the End of the Hopper, or against the Flanch) on the Outside of the Box or Hopper; and for that, the longer this Cylinder is, the better the Brass Spindle will turn in it.

_Fig._ 11. is the Spring-cover, with its Hole, whereby it is screwed into its Place, as it is seen marked A, in _Fig._ 9.

_Fig._ 12. is the Setting-screw pointing against its Hole, its Head being flat, that it may be turned by the Finger and Thumb.

_Fig._ 13. is the Counter-screw, to be turned in the same manner.

_Fig._ 5. shews the Brass Spindle of the Turnep Seed-box, and the Manner of turning it against its Steel Tongue, or Spring; which Manner is different from that of turning the larger Spindles for Boxes of a larger Size, such as the Wheat Seed-box.

This Spindle[266], being but half an Inch Diameter, is too small to be turned by the Two Wheels, as the larger Spindles are; not only because it would be in Danger of breaking by the Weight of the Hopper, and by the Twisting (or Wrenching) of the Wheels; but also because it would soon become loose, by wearing the hollow Cylinder thro’ which it passes; and it would be apt to open the Brass Flanches from the Bottom of the Hopper, whereby the Seed might run out, beside several other Inconveniencies; all which are prevented by turning the Spindle in the manner shewn in this Figure; for here the Spindle never presses against the hollow Cylinder, with any greater Force than that of its own Weight, which is so very little, that the Friction made by it is next to nothing.

[266] I believe, if it were less by a Fourth or Third of its Diameter, it might be better, as being more proportionable to the Smalness of the Turnep-seed. I have had the Mortise much wider; but it cannot well be made much narrower, whilst the Tongue is of this Fashion; for this Steel Tongue, if narrower, would either be too stiff, or else apt to break, nor would there be Room in the Mortise for a sufficient Setting-screw to follow it. But there is another Fashion, wherein a narrower Brass Tongue has a broad Spring behind it; and when it is in this Manner, the Mortise may be a Fourth of the Breadth of this. I have had many of these when I made my Boxes in Wood; but cannot describe them by these Cuts; neither are such narrow Mortises necessary, unless it were for drilling Tobacco seed, Thyme-seed, or some other Sort of an extraordinary Smalness.

A the Spindle, exactly fitting the Bore of the hollow Cylinder; which, when it enters the said Cylinder at its left End, in _Fig._ 9. will be stopped by the Wreath B B B; which Wreath, being circular, is cast on the Spindle, and is Part of it; the other End of the Spindle will then appear without the right-hand End of the said hollow Cylinder, at E in _Fig._ 9. and is kept there by the Wreath _Fig._ 14. which is to be put on upon the End of the Spindle, until it come to the Shoulder at _a_, which Shoulder is exactly even with the End of the hollow Cylinder; so that this Wreath will touch the End of the said Cylinder by its whole Surface. Then, to fix in this Wreath from coming off, we make use of the Slider, _Fig._ 15. whose Two Claws A, B, being thrust down by the Two Notches of the Spindle, at _b_ and _c_, until its other Part C, which is perpendicular to its Claws, comes down to the Flat of the Spindle, and environs one half of the Hole, covering the Part of the Flat which appears of a darker Colour; and then the upper Part of C, in _Fig._ 15. makes one level Surface with the Flat D of the Spindle; and then the Iron Fork E, being screwed into the Hole F, holds down the Slider fast, so that it cannot rise up; and then the Spindle, being in its Place, will run round without moving endways, being confined by these Wreaths.