Commonly used files can be divided into ordinary files and plastic files (assorted keys). Ordinary files are divided into flat files, square files, semi-circular files, triangular files and round files according to different cross-sectional shapes.

Threaded keys are often used in automobile maintenance. Mainly used to repair damaged threads.

Selection of files

The thickness of key tools should be comprehensively considered according to the properties of file materials, the size of machining allowance, machining accuracy and surface roughness. Coarse file is used for rough machining or filing non-ferrous metals; Machining with a file after rough machining; Fine files are used to file workpieces with small machining allowance and low surface roughness, while smooth files are only used to polish the final surface of workpieces.

In addition, according to the shape of the parts to be processed, choose files with different sections.

Square file has teeth on all sides, which can file square holes or process right-angle workpieces. A semicircular file can be used to file concave cambered surfaces.

Circular file can be used to file arc-shaped workpieces or large circular holes.

When choosing a file, the hardness of the file must be higher than that of the material before filing; Moreover, ordinary files cannot be used to file materials with low hardness, such as copper and aluminum, because copper and aluminum will block the file teeth.