Fig. 15.
When the saw is placed between these clamps and held together by the jaws of the vise, you are ready for the filing operation. Observe the following filing suggestions: Always hold the file horizontal or level. In filing, use the whole length of the file. Do the work by a slow, firm sweep.
Do not file all of the teeth along the saw at one operation, but only the alternate teeth, so as to keep the file at the same angle, and thus insure accuracy; then turn the saw and keep the file constantly at one angle for the alternate set of teeth.
Give the same number of strokes, and exert the same pressure on the file for each tooth, to insure uniformity. Learn also to make a free, easy and straight movement back and forth with the file.
The File.—In order to experiment with the filing motion, take two blocks of wood, and try surfacing them off with a file. When you place the two filed surfaces together after the first trial both will be convex, because the hands, in filing, unless you exert the utmost vigilance, will assume a crank-like movement. The filing test is so to file the two blocks that they will fit tightly together without rolling on each other. Before shaping and planing machines were invented, machinists were compelled to plane down and accurately finish off surfaces with a file.
In using the files on saws, however small the file may be, one hand should hold the handle and the other hand the tip of the file.
A file brush should always be kept on hand, as it pays to preserve files by cleaning them.