The surface of the workpiece is cut with a needle file to make it meet the shape, size and surface roughness required by the part drawing. This processing method is called filing, which is easy to process and has a wide working range. It is mostly used after chiseling and sawing. , Filing can process planes, curved surfaces, inner and outer arcs, grooves and other complex surfaces on the workpiece. The highest precision of filing can reach IT7-IT8, and the surface roughness can reach Ra1.6-0.8μm. It can be used for forming templates, mold cavities and components, and workpiece trimming during machine assembly. It is one of the main operation methods of fitters.

Second, the file

1. The material and structure of the file

The files are usually made of carbon tool steel T10 and T12, and are hardened to HRC62-67 by heat treatment.

The file is composed of a file surface, a file edge, a file tongue, a file tail, and a wooden handle. The size of the file is indicated by the working length of the file face. The teeth of the file are chopped on a chopper.

2. Types of files

Files are divided into three categories according to their uses: ordinary files (or fitter files), special files and plastic files (or assorted files). Among them, ordinary files are used the most.

Ordinary files are divided into five types according to different cross-sectional shapes: flat file, square file, round file, semi-circle file and triangular file; according to their length, they can be divided into seven types: 100, 200, 250, 300, 350 and 400mm; The tooth pattern can be divided into: single tooth pattern, double tooth pattern (mostly with double tooth pattern); according to its tooth pattern, it can be divided into: coarse tooth, fine tooth and oily file, etc. It is indicated by the number of teeth on the surface, 4-12 teeth for rough files, 13-24 teeth for fine files, and 30-36 teeth for glossy files).

3. Selection of files

Reasonable selection of files has a great influence on ensuring processing quality, improving work efficiency and prolonging the service life of files. The general principles for choosing a file are:

(1) Select the shape and specification of the file according to the shape of the workpiece and the size of the machined surface:

(2) Select the thickness of the file according to the requirements of the soft and hard processing material, machining allowance, precision and surface roughness. The rasp has a large tooth pitch and is not easy to block, and is suitable for rough machining (that is, with large machining allowance, low precision grade and surface quality requirements) and filing of soft metals such as copper and aluminum; fine files are suitable for steel, cast iron and surface quality. Filing of workpieces with high requirements; glossy files are only used to polish the processed surface. The finer the file, the smoother the surface of the workpiece, but the lower the productivity.

Three, filing operation

1. Clamp the workpiece

The workpiece must be firmly clamped in the middle of the jaws of the vise. The surface to be filed is slightly higher than the jaws, but not too high. When clamping the processed surface, a copper sheet or Aluminum sheet.

needle file