What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
When the countersunk head screws and hexagon socket head bolts are produced by the cold heading process, the original structure of the steel will directly affect the forming ability of the cold heading process. In the process of cold heading, the plastic deformation of the local area can reach 60%-80%, so the steel must have good plasticity. When the chemical composition of the steel is constant, the metallographic structure is the key factor to determine the plasticity. It is generally believed that the coarse flaky pearlite is not conducive to cold heading forming, while the fine spherical pearlite can significantly improve the plastic deformation ability of the steel. For medium carbon steel and medium carbon alloy steel with a large amount of high-strength bolts, spheroidizing (softening) annealing is performed before cold heading, so as to obtain uniform and fine spheroidized pearlite to better meet the actual production needs. For the softening annealing of medium carbon steel wire rods, the heating temperature should be kept above and below the critical point of the steel, and the heating temperature should not be too high, otherwise tertiary cementite will precipitate along the grain boundary, resulting in cold heading cracking. The wire rod of medium carbon alloy steel is annealed by isothermal spheroidization. After heating at AC1+ (20-30%), the furnace is cooled to slightly lower than Ar1, the temperature is about 700 degrees Celsius for an isothermal period, and then the furnace is cooled to about 500 degrees Celsius and air-cooled. The metallographic structure of the steel changes from coarse to fine, from flake to spherical, and the cracking rate of cold heading will be greatly reduced. The general area of softening annealing temperature for 35\45\ML35\SWRCH35K steel is 715-735 degrees Celsius; while the general heating temperature for spheroidizing annealing of SCM435\40Cr\SCR435 steel is 740-770 degrees Celsius, and the isothermal temperature is 680-700 degrees Celsius.
hand screw is a screw with a plastic head, and the user fixes the hand screw by turning the plastic head by hand. At present, a hand screw is disclosed in the market publication number CN202203253U, which includes a plastic head and a screw rod, the plastic head and the screw rod are connected together, and the height of the plastic head is higher than that of an ordinary screw, and the height is 12 cm. The screw of the hand screw is fixed in the plastic head by glue. After a period of use, the aging of the glue leads to the loosening of the screw and the plastic head. When the plastic head is stressed, the screw rod comes out of the plastic head, which affects the normal use of the hand screw.
Heat resistance refers to both the oxidation resistance or gas medium corrosion resistance at high temperature, that is, thermal stability, and at the same time, it has sufficient strength at high temperature, that is, thermal strength. As the material requirements of products produced by customers are getting higher and higher, the requirements for screws used in product materials are also getting higher and higher. When product materials face harsh environments and special occasions, more and more high-quality mechanical properties of stainless steel screws are used. Therefore, stainless steel screws were selected. The requirements are getting higher and higher, and the material of stainless steel screws is getting higher and higher. Therefore, many ordinary stainless steel screws SUS201 are replaced by stainless steel SUS304 screws and stainless steel screws SUS316. Of course, if some requirements are not so high, general customers will choose stainless steel screws SUS201, which are relatively cheap in cost.
rivet nut is a tool for riveting nuts, which can be used for riveting the nut to a sheet and has a wide range of uses. Most of the existing rivet nuts have a double-handled structure, which is complicated in structure and high in cost; and the double-handled structure generally requires both hands to operate due to the large distance between the two handles, which is inconvenient to operate. Technical realization elements: In order to solve the above technical problems, Yueluo provides a rivet nut with simple structure, low cost and convenient operation. The technical solution adopted by Yueluo is: including a fixed body, a sliding body, a guide sleeve, a nut, a hollow screw and a handle;
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