Files are divided into ordinary files, special files and plastic files (assorted files). Generally divided into square files, triangular files and so on. Special files with many shapes. You can check for yourself. The size, diameter and length of plastic file are 4 mm and 160 mm respectively, which are generally used for the correction of metal processing. File rough file is used for machining allowance of 0.5-1mm. The machining allowance of medium file is between 0.2 and 0.5. The allowance of fine file is between 0.05 and 0.2, and the surface roughness can reach RA 1.6. File is used to cut the surface of the workpiece, so that the workpiece can reach the required size, shape and surface roughness \x0d\ The thickness of the file depends on the pitch (pitch). The tooth thickness of the file can be divided into the following types: \x0d\ 1 # pattern: used for coarse-toothed files, with a tooth pitch of 2.3 ~ 0.83mm..\ x0d \ pattern: used for medium-toothed files, with a tooth pitch of 0.77 ~ 0.42mm..\ x0d \ pattern: used for fine-toothed files, with a tooth pitch of 0. The tooth pitch is 0.25 ~ 0.2mm. \ x0d \ pattern: used for smooth file, the tooth pitch is 0.2 ~ 0. 16mm.