What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Material and process requirements The self-tapping locking screw should be made of high-quality carburized steel cold heading, generally no larger than M12. The finished material should be drawn with a high total reduction rate before cold heading, so that the cold heading must be spheroidized. Annealing, in order to enhance the surface hardness and the toughness of the core, most of them are made of medium and low carbon steel. The chemical composition of the material in the standard is only for guidance. The C content is 0.13%~0.37%, the Mn content is 0.64%~1.71%, and the B content can reach 0.005%. The elements of S, P, Mn and Si in the commonly used steel are generally lower than those of the ordinary bolt steel of the same grade. And the surface quality of the material is strictly controlled to reduce deformation resistance and prevent deformation and cracking. Commonly used grades are 20Mn, 15MnB, SWRCH22A, 1022A and medium carbon steel, medium carbon alloy steel SWRCH35K, SCM435, SCR435, etc. Self-tapping locking screws are threads with an arc-shaped triangular cross-section, so the formulation of cold heading and wire rolling processes, as well as the design and manufacture of cold heading dies and special rolling plates are very important. Self-tapping locking screws require a high-hard surface for cutting and extruding capabilities due to the need for self-tapping low carbon steel. At the same time, there must be sufficient core strength and toughness to prevent twisting and breaking during work. The heat treatment process of this type of screw belongs to shallow carburizing. Regardless of whether it is made of low carbon steel or medium carbon or medium carbon alloy steel, its core hardness must be guaranteed to be within the range of 28~38HRC (9.8 grade) 33~39HRC (10.9 grade) and not less than the minimum tensile load of 930MPa (9.8 grade), 1040MPa (grade 10.9), depending on the material, the minimum tempering temperature is 420℃. In order to ensure that the self-tapping locking screw can be smoothly screwed into the prefabricated cylindrical hole, the end of the screw should be hardened by high-frequency quenching to ensure that at least one to three thread teeth are hardened, and the minimum surface hardness is 45HRC.
With the advancement of technology in various industries, the current structural design of screws has evolved from just simple locking to focusing on work efficiency during the locking process and not destroying the integrity of the objects to be locked. New cases such as No. 556784 screw improvement and No. 289415 screw that integrates locking, stability, labor-saving, fast and multi-function which were previously designed and approved and published in the Central Taiwan Bulletin are the main representatives of screws. It is clear that It is learned that the two cases not only fully improve the shortcomings of the traditional simple locking screws, but also achieve the purpose of substantial improvement of the screws designed in each case in actual use.
The material of the second combination screw: It is decided to use the test machine to test the material of the combination screw wire, which is divided into iron and stainless steel. Iron wire is divided into 1010 wire and 1018 wire, 10B21 wire, etc., stainless steel is divided into stainless steel 201, stainless steel 304, stainless steel 316 and so on. The provisions of the national label of three combination screws: Generally, those who have experience in combination screws can be separated by using the inner eye. The difference between hexagon heads. Use a caliper to measure out the three-combination screw specifications. How big is it, how long is it, how thick is the head of the combination screw, how thick is the flat washer, and what is the outer diameter of the flat washer. How many hours is the salt spray of the combination screw measured with a salt spray machine. Use the environmental test machine to test whether the three-combination screw is environmentally friendly. Still not environmentally friendly.
At present, the convex washers with traditional structures on the market have unreasonable designs and complex structures, and are inconvenient to install and disassemble. After long-term use, they are prone to fracture and deformation due to poor toughness, resulting in short service life and requiring regular downtime for maintenance, affecting assembly. The working efficiency and safety of its equipment are also poor in terms of wear resistance, corrosion resistance, and high temperature resistance. Regular replacement and maintenance also increase the economic cost of production. Therefore, the convex gasket of the existing structure can no longer meet the existing mechanical requirements. The high standard use requirements of assembly auxiliary parts are urgently needed to be solved at present.
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