The mesh number of a file is expressed by how many small teeth there are in a 1cm square area. The mesh number refers to the particle size or thickness of the material. The general definition refers to the screen within the area of ​​​​1 inch * 1 inch, the material can pass through the screen, and the number of holes in the screen is defined as the mesh number. Such as 200 mesh, that is, the material can pass through a screen with 200 meshes within 1 inch * 1 inch. By analogy, the larger the mesh number, the finer the material particle size; the smaller the mesh number, the larger the material particle size. The sieving particle size is the size of the sieve holes that the particles can pass through the screen . The specifications of standard sieves vary from country to country. The commonly used Taylor system uses the number of holes per inch as the sieve number, which is called mesh. For example, a 100 mesh sieve means there are 100 sieves per inch of screen .

In the heat treatment process of the steel file, the hardness of 45# steel after quenching can reach up to HRC55+, but it must be tempered when it is generally used. The hardness after heating surface quenching will be higher.

For the maintenance of the file, use one side of the new file first, and then use the other side when it is blunt; when filing rough, the effective full length of the file should be fully used to avoid local wear; the file should not be stained with oil or water; when filing, If the filings are embedded in the tooth gap, the cuttings on the filing teeth must be removed with a wire brush in time; the hard skin of the rough piece and the hardened workpiece should not be be filed, and the soft metal such as aluminum and tin should be filed, and a single-tooth file should be used; If there is a hard skin on the surface of the casting, you should use an old file or the toothed side of the file to remove the hard skin before processing; the file must be cleaned after use to avoid rusting; it should not be used with other tools or workpieces. Stack them together, and do not overlap with other files, so as not to damage the teeth.

File structure, classification, selection, filing posture, filing method and quality inspection. First of all, it is necessary to hold the file correctly. Keeping the straight motion of the file when filing the plane is the key to filing. The filing force includes horizontal thrust and vertical pressure. When the file is advanced, the pressure of the front hand gradually decreases, the pressure of the back hand is large, and the pressure of the back hand is small. When the file is pushed to the middle position, the pressure of both hands is the same. When the file is continued to advance, the pressure of the front hand gradually decreases and then the pressure increases. No pressure is applied when the file is returned. This makes it easier for us to file. Then there are scraping, grinding, drilling, reaming, tapping and so on.