The many kinds of files are classed according to (1) length; (2) form of teeth, and (3) shape of cross section of the body of the file.

The usual forms of teeth are classified as shown in Fig. 207. There are finer-toothed files than the " smooth," the most used of which is the " dead smooth."

In cross-section, the usual shapes are (a) rectangular, including mill, flat, pillar, square and warding; (b) round or partly round,

Rasp.

Coarse. Double Cut.

Coarse. Single Cut.

Coarse.

Bastard.

Bastard.

Bastard.

Second Cut.

Second Cut.

Second Cut.

Smooth.

Smooth.

Smooth.

Fig. 207. - Styles of File Teeth.

including half-round, crossing, tumbler, pit-saw, cabinet cross-cut and round; and (c) triangular, including three-square, and knife-edge. Some rectangular files are smooth on one or both edges, and mill or flat files may have slightly rounded edges. Fig. 208 shows the cross-section shape of files most used. These are:

(1) Flat.

(2) Mill.

(3) Pillar.

(4) Warding.

(5) Square.

(6) Pound.

(7) Half-round.

(8) Three-square.

(9) Knife-edge. (10) Cabinet.

In length (measured from the heel, or where the tang begins) files may be blunt or tapered, and the usual lengths of machine-shop files vary from 3 to 20 inches. Smaller sizes of files for special uses are known as needle files.

Another type of file has recently come to the notice of machinists. This is a single-cut file with the cuts arranged in arcs across the length of the file.

Fig. 208. - Cross Sections of Files.