Files are divided into ordinary files, special files and plastic files (assorted files). Ordinary files are divided into square files and triangular files. Special files with many shapes. You can check for yourself. Plastic files are usually used for metalworking correction. The machining allowance of rough file is 0.5- 1 mm, and that of medium file is 0.2-0.5. The surface roughness can reach RA 1.6. File is used to cut the surface of workpiece to make the workpiece reach the required size, shape and surface roughness.

The thickness of the file is determined by the pitch of the teeth. The tooth thickness of the file is divided into the following categories:

1 pattern: used for coarse tooth files, with a pitch of 2.0.83mm 。

No.2 grain: use a middle tooth file with a pitch of 0.77 ~ 0.42 mm.

No.3 grain: used for fine-tooth files, with a pitch of 0.33 ~ 0.25mm. 。

No.4 grain: used for double fine tooth files (sometimes called smooth file), and the tooth spacing is 0.25 ~ 0.2 mm.

No.5 grain: used for smooth file, with the pitch of 0. 0.16mm.