File Handles

The handles commonly attached to files are of wood and are made to fit the hollow of the hand. The handle is driven onto the tang of the file, a ferrule on the handle preventing it from splitting. Care should be taken to have the axis of the handle parallel with the file. A good way to prepare the handle for the tang is to heat the tang to a dull red, the file proper being kept cool by a piece of wet cotton waste, and the hole in the handle burned out until the tang is almost in the position it is designed to finally occupy. After cooling the tang, very little driving will be required to securely fasten the handle to the file.

When filing surfaces of such size that the handle as ordinarily applied would interfere with, the use of the file, the tang may be bent up to an angle so that the handle will clear the surface. Various forms of holders are used for filing under these circumstances, the simplest forms being shown in Fig. 52.

Correct Filing Position

The correct position for filing is about as follows: feet about 8 inches apart and at right angles, the left foot being in line with the file; stand back from the vise so that the body may follow the file slightly; grasp the file handle with the right hand, fingers below, thumb on top of, the handle. For coarse filing, place the ball of the thumb of the left hand on the point of the file, and for fine filing grasp the point of the file with the thumb and forefinger of the left hand, Fig. 53. When holding the file in one hand, as is often done in light work, the forefinger should be on top of the file, pointing in the direction of its length, as is shown in Fig. 54. This allows free movement of the hand and wrist, pressure being applied principally by the forefinger.

Fig. 53. Bench Filing Position.

As file teeth or cutting edges point toward the end of the file, it is evident that the file can cut only when moving in a forward direction. On the return stroke, the pressure should be relieved; otherwise the teeth will be dulled when drawn back over the surface.

Choice of Files Depends on Work

The kind of metal being worked determines in a great measure the character of the file to be used. Cast iron, especially if the scale has not been previously removed, is particularly hard on a new file, as the glassy character of the scale tends to dull the cutting edges. New files should never be used on such a surface. It is found that on tool steel, and on hard materials generally, a second-cut file is better than the bastard. This is because if pressure enough is exerted to cause the coarse teeth of the bastard to bite into the work, the teeth, being comparatively long, are very likely to be broken off. In the second-cut file, the teeth are shorter and present more cutting points in a given area, thus preventing excessive duty being imposed on a few teeth.

Fig. 54. Position for Single Hand Filing.

Softer metals, such as brass and bronze, allow the use of the coarser grades.