1. Selection of file section shape

The cross-sectional shape of the file should be selected according to the shape of the parts to be filed, so that the shapes of the two can be adapted. When filing the inner arc surface, choose a semicircular file or a round file (small diameter workpiece); when filing the inner corner surface, choose a triangular file; when filing the inner right angle surface, you can choose a flat file or a square file, etc.

When choosing a flat file to cut the inner right-angle surface, pay attention to make the narrow surface (smooth edge) of the file without teeth close to one surface of the inner right-angle, so as to avoid bumping the right-angle surface.

2, the choice of file tooth thickness

The thickness of the file teeth should be selected according to the machining allowance, machining accuracy and material properties. Coarse-tooth files are suitable for machining workpieces with large allowances, low dimensional accuracy, large geometric tolerances, large surface roughness values, and soft materials; otherwise, fine-tooth files should be selected.

When using, it should be selected according to the machining allowance, dimensional accuracy and surface roughness required by the workpiece.

3. Selection of file size specifications

The size of the file should be selected according to the size and machining allowance of the workpiece to be processed. When the processing size is large and the allowance is large, a file with a large size should be used, otherwise, a file with a small size should be used.

4. Selection of file tooth pattern

The tooth pattern of the file should be selected according to the nature of the workpiece material being filed. When filing soft material workpieces such as aluminum, copper, and mild steel, it is best to use a single-tooth (milling tooth) file. The single-tooth file has a large rake angle, a small wedge angle, a large chip flute, and the chips are not easily blocked, and the cutting edge is sharp.