Part 3
If the lathe is not provided with a compound rest, this angle may be cut by setting a square-nose tool, as in Fig. 31, with the aid of a thread gauge. Any other angle would have to be set with a bevel and bevel protractor.
[Illustration: Fig. 31]
This tool is not as wide as the surface to be cut because one that will cut the full width is very liable to chatter. It is therefore better to make several cuts with a narrow tool. The surface can then be finished smooth by filing.
The closeness of the fit of this taper with that in A can be tested by rubbing black paint, which consists of lamp black and oil, on the tapered surface in A. When B is screwed into A, marks will be made on B indicating the high spots. If these are not too high, they may be removed by filing.
FINISHING OUTSIDE OF PIECE A.
Piece A may now be screwed on B and the outside rough turned to within ¹⁄₃₂ of an inch of the finished size.
The ends of the different steps are finished to the proper length with the tool shown in Fig. 29. This same tool can then be used to turn the different diameters to within 0.002 or 0.003 of an inch of the required size. These steps are brought to the final size by filing.
=Filing.=—The file for this work should be less than 1 inch in width. If it is wider than the steps, a beginner will usually file the portion at the end of each step smaller in diameter than that which is close to the square corners.
The different diameters may be measured accurately with the micrometer calipers.
KNURLING
After piece A is finished, it is removed from B and B is reversed in the lathe so that the boss may be knurled.
In case there is enough room between the dog and the work, when held as in Fig. 30, there is no need to reverse the work for knurling since it can be done in this position.
The boss at the end of B is used as a handle so that if it were left smooth it would be hard to turn by hand. The surface is therefore made rough with a knurling tool as shown in Fig. 32.
[Illustration: Fig. 32]
The speed of the lathe should be about the same for knurling as for thread cutting. If the lathe runs too fast, the knurling tool does not cut satisfactorily.
The tool is set so that the face of the rollers is parallel with the surface to be knurled. When starting the cut, the rollers can be forced into the piece easier if about half of their width extends past the end of the work.
The knurling tool should be pressed into the work fast enough so that about one half the depth of the finished knurl will be cut while the lathe makes three or four revolutions. If the tool is forced in too slow, it will cut a finer knurled surface than the rollers are intended to cut.
The tool is fed along the surface in the same manner as in plain turning. The speed at which the carriage of the lathe moves has no effect upon the pitch of the knurled surface since this is controlled by the pitch of the grooves in the rollers. If a finer knurled surface is desired, a knurling tool having rollers with finer grooves would have to be used.
TRANSCRIBER’S NOTE
Illustrations in this eBook have been positioned between paragraphs and outside quotations.
Obvious typographical errors and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources.
Some hyphens in words have been silently removed, some added, when a predominant preference was found in the original book.
Except for those changes noted below, all misspellings in the text, and inconsistent or archaic usage, have been retained.
Pg 9: ‘straght’ replaced with ‘straight’ Pg 11: ‘shoull’ replaced with ‘should’ Pg 19: ‘diffrent’ replaced with ‘different.’