File. A tool used by most workers in metal to give the required shape to the pieces they work on. Almost always a long piece of tempered steel, as hard as possible, with the surface cut in various directions into a great number of small teeth similar to those of a ratchet in clockwork, with their base on the body of the file.

According to the use intended for them, files have different sizes, thicknesses and shapes. There are three classes, namely: coarse files ; bastards, with a much finer cut; and fine, which are still finer.

Horologists are the greatest users of files . The ones most especially suited to these craftsmen are:

1) Vee file , Plate [XIV, Figure 32], use for various purposes, particularly to deepen the threads of the endless screw.

2) Oval file , [Figure 33], pointed, and rounded on both sides. Particularly useful for the arms of wheels, balances, etc.

3) Flat file , [Figure 34], with various uses.

4) Offset files , whose shapes are shown after the preceding ones [Figures 28-30] allow filing in places where a straight file could not reach, as in cases, bells, etc.

5) Half-round file [Figure 35] used to round various parts, particularly wheel teeth or pinion leaves.

6) Dressing file [Figure 36] used to round the leaves of a pinion.

7) Pivot file [Figure 37], very fine, used to turn pivots on the lathe.

8) Dressing files , very small, very fine flat files used to equalize the slots between the teeth, and to square the bottom or notch.

9) Insert files , for making the slots in the potence where the inserts fit, and other parts assembled with dovetails.

10) Back files [Figure 27], for equalizing, adjusted by means of two or three screws between two plates that are very straight and of equal length; the edges of the plates may project more or less. This kind of file is used to equalize the depth of all the teeth on a wheel, by filing the bottom of the slots until all the teeth touch the edges of the back.

11) Offset files [Figure 44] for turning the pivots of the contrate wheel; they are hook-shaped, as shown in the figure, because the pivot that turns in the potence is in the hollow of the contrate wheel, so it would be impossible to turn with a straight pivot file when the wheel is mounted.

12) Contrate wheel files , to file the tooth surfaces on that wheel.

Finally, files for filing and smoothing the inner edges of wheels so designed, by means of the half-round part.

The name file is also given to pieces of metal having the same shape, used for polishing; they may be of tin, brass, or steel.

All files have handles, as illustrated, of wood, with a brass ferrule.