The file is made of carbon tool steel T 12 or T 13. After heat treatment, the hardness of the cutting part reaches HRC 62 ~ 72. It is a standard tool produced by professional factories.

2, the structure of the file

The file consists of a file body and a file handle.

(1) File body includes file surface, file edge and file tail.

(1) File surface refers to the upper and lower sides of the file, which is the main working surface. The front end of the file face is made into a convex arc, and there are file teeth on both sides, which is convenient for filing. The file is also made into a longitudinal convex arc, which can offset the surface bulge caused by the up-and-down swing of both hands during filing and make the workpiece smooth.

(2) File edge refers to two sides of the file, which are divided into tooth edge and smooth edge. The tooth edge can be used for cutting, and the smooth edge only plays a guiding role. Some files have no teeth on both sides, while others have teeth on one side. The toothless side is called the smooth edge, and its function is to file the other right-angled side with the smooth edge against the machined surface when filing the inner right-angled surface, so as to prevent the machined surface from being damaged.

③ The file tail (tongue) is used to fix the file handle. The file tongue is not quenched.

(2) The function of the file handle is to facilitate holding and transmitting thrust when filing. Generally, it is made of wood, and one end of the mounting hole should have an iron hoop.

3, file teeth and file lines

(1) File tooth: File tooth is the type of tooth used by file to cut. When filing, each file tooth faces the chisel to cut the metal material.

① There are two kinds of tooth profiles of file teeth: cutting teeth and milling teeth. Chop the teeth with a file cutter, and milling the teeth with a gear milling method. Tooth-cutting file is easy to process and has low cost, but the cutter teeth are blunt and the filing resistance is large, but the cutter teeth are not easy to wear and can cut hard metals. Milling gear file is time-consuming and expensive, but the cutter teeth are sharp. Because the cutter teeth are easy to wear, they are only suitable for cutting soft metals.

② The thickness specification of the file teeth is expressed by the tooth pitch of the file teeth. Large pitch, for coarse files, small pitch, for fine files. Its thickness is divided into the following categories:

Coarse file adopts 1 file pattern with a pitch of 2.3 ~ 0.83mm..2 No.2 file pattern is used for medium coarse file with a pitch of 0.77 ~ 0.42mm, No.3 file pattern is used for fine file with a pitch of 0.33 ~ 0.25mm. No.4 file pattern is used for double fine file with a pitch of 0.25 ~ 0.20 mm, 5. ..

(2) File pattern: File pattern is the pattern of file teeth arrangement, including single tooth pattern and double tooth pattern.

① Single tooth pattern refers to the tooth pattern with only one direction on the file. Suitable for filing soft materials.

The single tooth line is mostly milled and the rake angle is cut. The strength of the teeth is weak, and the whole tooth width is cut at the same time. The chips removed by filing are not fragile, even as wide as the file, so the cutting resistance is large and a lot of cutting force is needed. Therefore, it is only suitable for filing soft materials and narrow-faced workpieces.

(2) Double tooth pattern refers to the tooth pattern arranged in two directions on the file. Suitable for filing hard materials.

Most of the double tooth patterns are broken teeth, the first is the bottom tooth pattern (shallow tooth pattern) and the second is the top tooth pattern (deep tooth pattern). The direction and angle of the upper and lower tooth lines are different, so the teeth formed in this way are inclined and regularly arranged along the center line of the file. When filing, the file marks of each tooth are staggered and not overlapped, and the file surface is smooth. When filing, chips are broken, which reduces cutting resistance and saves labor. The strength of the file teeth is also high, which is suitable for filing hard materials and wide-faced workpieces.

4. File type

Archives are usually divided into three categories: ordinary archives, special archives and plastic archives. According to the machining method of cutter teeth, file can be divided into two types: chopping file and milling file. According to the arrangement of file teeth, it can be divided into single-tooth file and double-tooth file; According to its processing object, it can be divided into three types: ordinary file, special file and plastic file.

(1) Common files are mainly used for processing common workpieces. According to the different section shapes, it can be divided into five types: flat file (plate file), square file, triangular file, semi-circular file and round file. So as to be suitable for processing different surfaces.

According to the number of tooth lines per 10mm length, ordinary files can be divided into coarse teeth (4 ~ 12 teeth), fine teeth (13 ~ 24 teeth) and smooth teeth (30 ~ 40 teeth).

(2) Special files are used to process the special surfaces of parts. There are knife-edge files, diamond-shaped files, flat triangular files, oval files, round belly files and so on.

(3) Plastic files (group files or assorted files) are mainly used for processing small parts and narrow faces, finishing molds and templates, and trimming small parts on workpieces. The length and cross-sectional size of plastic files are very small, and the cross-sectional shapes are round, equilateral triangle, rectangle, semicircle and so on. It is named because it is equipped with small files with various cross-sectional shapes. Usually each group consists of 5, 6, 8, 10 or 12.

5. Specifications of documents

The specification of the file is generally expressed by the length of the toothed part of the file. Commonly used plate gears are 100mm, 150mm, 200mm, 250mm and 300mm. File size specification, different files have different parameters. The size and specifications of circular files are expressed in diameter, the specifications of square files are expressed in square size, and other files are expressed in file body length.

6. Selection of files

The reasonable selection of archives has great influence on improving the efficiency, ensuring the quality and prolonging the service life of archives. Each file has its specific purpose, and the appropriate file must be carefully selected before filing. If the selection is improper, it will not give full play to its efficiency or lose its cutting ability prematurely, and the filing quality cannot be guaranteed.

The correct selection of files should be considered from the following aspects according to the specific situation of the processing object:

(1) The section shape of the file should be adapted to the shape of the workpiece.

(2) Coarse file is selected for rough machining and fine file is selected for finishing. Rough file is suitable for filing workpieces with large machining allowance, low machining accuracy and large surface roughness. Fine filing is suitable for filing workpieces with small machining allowance, high machining accuracy and small surface roughness. Single-tooth file is suitable for processing soft materials.

The choice of file thickness depends on the properties of workpiece material, machining allowance, machining accuracy, surface roughness requirements and hardness of workpiece material. Rough file (or single-tooth file) is not easy to block because of its large pitch and chip space. It is suitable for filing workpieces with large machining allowance, low machining accuracy and large surface roughness and soft metal materials such as copper and aluminum. Fine filing is suitable for filing workpieces with small machining allowance, high machining accuracy and small surface roughness, and also suitable for filing steel, cast iron and so on. Polishing file is used in the final finishing to make the surface of the workpiece smooth, so as to improve the dimensional accuracy and reduce the roughness.

(3) The length of the file should generally be longer than the file surface 150 ~ 200mm. The size of the file depends on the size of the machined surface of the workpiece and the machining allowance. When the size of the machined surface is large and the machining allowance is large, a longer file should be selected; Otherwise, choose a shorter file. The length of the file should generally be longer than the file surface 150 ~ 200mm.