No. 2. Square file, which may be tapering from end to end, or have parallel sides throughout.
No. 3. Watch pinion file. This may have its sides parallel or tapering, to make a knife-shaped file.
No. 4. Clock-pinion; which may be used for either nicking, piecing, or squaring-off purposes.
No. 5. Round, with parallel sides for gulleting purposes, or rat-tail when it tapers.
No. 6. Triangular, or three equally-sided body for saw filing. [p. 57]
No. 7. Equalizing file. This is parallel when used for making clock-pinions or endless screws; or for slitting, entering, warding, or making barrel holes, when the body of the file tapers.
No. 8. Cross, or double-round, half-file.
No. 9. Slitting file; which has parallel sides only. A cant file.
Character of the File Tooth.—Files are distinguished principally by the character of the oblique, or cross grooves and ridges which do the cutting and abrading when the file is drawn across the surface.
This is really more important than the shape, because the files, by their cuttings, are adapted for the various materials which they are to be used upon.