What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Please refer to FIG. 1 , which is a cross-sectional view of a conventional screw and screw washer for locking two metal parts. The screw 100 is combined with the screw washer 110 to lock the metal parts 120 and 130 . The screw washer 110 includes a washer portion 112 and a body washer portion 114 . The washer portion 112 is used for electrically isolating the screw head 102 from the metal piece 120 , and the screw body washer portion 114 is used for electrically isolating the screw body 104 and the metal piece 120 . Therefore, through the design of the screw washer 110 , the screw 100 can be isolated from conducting the metal parts 120 and 130 .
1. The twisted screw should be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw should be given according to the normal clearance with the barrel. 2. After the thread surface with the reduced diameter of the worn screw is treated, the wear-resistant tungsten carbide alloy is thermally sprayed, and then ground to size. 3. Surfacing wear-resistant tungsten carbide alloy on the thread part of the worn screw. According to the degree of screw wear, surfacing welding is 1~2mm thick, and then the screw is ground and processed to size. This wear-resistant tungsten carbide alloy is composed of materials such as C, Cr, Vi, Co, W and B, which increases the wear resistance and corrosion resistance of the screw. 4. The bottom diameter of the screw is repaired by electroplating hard chromium. Chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easier to fall off.
The traditional fixture shown in Figure 2 is composed of a hardened support cylinder and a hardened shear bar, and has a simple structure. The cylindrical pin is loaded into the hardened support cylinder, and the shear test is completed by applying an axial load to the hardened shear bar. Since the standard stipulates that the gap between the loading part and the supporting part does not exceed 0.15mm, in order to ensure the matching of the gap during the shear test of the cylindrical pin, the diameter of the cylindrical pin on the cylinder is generally equal to the theoretical cylindrical pin. In practical application, the cylindrical pin is irregular in size after heat treatment. To realize the shear test, the cylindrical pin must be inserted into the hole with the help of external force, which is difficult to install and clamp and takes a long time. If the double-sided shearing is performed, that is If the cylindrical pins need to be installed on both sides, the time is doubled, and the notch of the cylindrical pins cannot be guaranteed to face upwards.
Screw refers to a screw, which is a tool that uses the physical and mathematical principles of the inclined plane, circular rotation and friction of an object to gradually fasten objects and parts. A screw is a common term for fasteners. Fasteners are widely used in machinery, electrical appliances and buildings. They are generally made of metal or plastic, cylindrical in shape, and grooves engraved on the surface are called threads.
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