What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Cylindrical pins are generally used to connect, lock parts or for assembly positioning, and can also be used as parts of safety devices. The cylindrical pin is fixed in the pin hole by interference fit with the pin hole to fix parts, transmit power, or act as a positioning member. The prior art cylindrical pin press-fitting is shown in Figure 1. This kind of cylindrical pin prevents the cylindrical pin body from withdrawing through the locking force and axial friction force brought by the interference fit between the cylindrical pin body and the pin hole. However, the interference of the cylindrical pin body will gradually decrease during use, so that the firmness of the connection and the positioning accuracy will gradually decrease. Therefore, the cylindrical pin can be easily withdrawn during use, resulting in potential safety hazards.
Blind rivets (blind rivets) --------- rivet body (rivet body) mandrel (rivet stem or rivet mandrel). It is a type of rivet for single-sided riveting, but it must be riveted with a special tool - a rivet gun (manual, electric, pneumatic). When riveting, the rivet core is pulled by a special rivet gun to expand the rivet body and play a riveting role. This type of rivet is especially suitable for riveting occasions where it is inconvenient to use ordinary rivets (riveting from both sides), so it is widely used in construction, automobiles , ships, aircraft, machinery, electrical appliances, furniture and other products. Among them, the open-type oblate head blind rivets are the most widely used, the countersunk head blind rivets are suitable for riveting occasions where the surface needs to be smooth, and the closed blind rivets are suitable for riveting occasions that require high load and certain sealing performance.
Now the screw itself is made of metal, so it is easy to rust, especially screws in harsh weather environments that are exposed to the air for a long time, such as air conditioners, wires, etc. In the existing technology, the shape of the screw has been fixed, and the structure of the screw itself is composed of a shaft with twill in the middle and a polygonal structure with stripes on the outside. OK, but because of the installation of some equipment, it needs to be exposed to the air for a long time. For example, the outdoor unit of the air conditioner must be installed in the outdoor area, and the outdoor can not be sheltered from wind and rain, so after long-term sun and rain, the screw The surface is easy to rust. If the rust is serious to a certain extent, the nut will be embroidered to death. Once the external machine needs to be disassembled one day, the embroidered screw will lose its use value and give workers to the workers. The disassembly and assembly of the screw has caused a lot of trouble, because the embroidered screw cannot be unscrewed directly. The only method used is to cut off the shaft in the middle of the screw with a hacksaw, or discard the entire screw structure. Since the shaft in the screw has been inserted into the middle of the wall, this waste is not good for both aesthetics and safety. To solve the rust problem of the screw, the existing technology is to improve the material of the screw, or to maintain it regularly, but this method itself is time-consuming and labor-intensive, and it is a waste of resources.
At present, the nut is used as the main body through the riveting connection with the gasket, which is more and more widely used in the industrial field, especially the automobile industry. The gasket connected with the nut has two types: spring gasket and flat gasket. After the nut is tightened, the washer gives the nut an elastic force, which is pressed against the nut to make it not easy to fall off; and the function of the flat washer is to increase the contact area between the nut and the coupling, increase the friction force, reduce the pressure per unit area and protect the surface of the connected parts. Not damaged, stop the nut from loosening. Therefore, gaskets have a wide range of applications in the field of fastening connections, and it is more and more important to improve production efficiency, reduce production costs, and meet growing demands.
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