What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The isolating switch in the substation has a large workload for maintenance. The transmission parts such as the isolating switch connecting rod are mostly connected by cylindrical pins. The shaft-pin fit is generally 1mm, which is tight. If the cylindrical pin is disassembled during the maintenance process, it is often due to corrosion and mechanical deformation. It is difficult to proceed smoothly for other reasons, and if the working environment is a small space, it is more difficult to disassemble. In traditional operations, grinding, hard prying, or beating with a hand hammer are often used to disassemble, which will further deform the pins, and when the space is small, it is difficult to use tools such as hand hammers. solve.
Now people often use spring washers to lock nuts and bolts, spring washers, generally stainless steel and carbon steel non-closed spiral washers, under the nut, above the flat washer, increase the friction between the nut and the bolt, used to prevent The loosening of the nut plays a role in preventing vibration and loosening, but it is often due to a radial external tension, which is caused by the tightening axial force generated by the tightening torque, and the phenomenon of open ring expansion occurs, and the hydrogen embrittlement of the spring washer often occurs. The pressure is unevenly applied to the flat washer through the spring washer, and the friction coefficient between the spring washer and the nut and the flat washer is small, resulting in vibration, rotation and relaxation.
At present, machinery and equipment have gradually become the main force of work production. Many equipment require frequent maintenance and even replacement of parts during use. During the process of maintenance and replacement, it is inevitable to encounter the problem of screw disassembly and assembly. In the process of disassembly and assembly, it is almost necessary to cooperate with both hands, or because the thread is too long, installation and disassembly are very cumbersome. Especially in the butt installation of flanges, bolts and nuts are used for clamping and fixing at this stage. During use, two hands are required to hold a board, a fixed screw, and a screw nut. This is to prevent the nut from During the turning process, the screw also rotates. When screwing, the wrench should be taken down without interruption, re-selected a good position, and then screw the screw forcefully again, and repeated several times before the screw can be unscrewed. Time and labor costs for maintenance are wasted. At present, there is no screw that is easy to install and remove.
Fasteners are a type of mechanical parts that are used for fastening connections and are widely used. All kinds of fasteners can be seen on all kinds of machinery, equipment, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, meters and supplies. It is characterized by a wide variety of specifications, different performance uses, and a very high degree of standardization, serialization and generalization. Therefore, some people also refer to a type of fasteners with existing national standards as standard fasteners, or simply as standard parts. Fasteners are the most widely used mechanical foundations. With my country's entry into the WTO in 2001, it has entered the ranks of major international trade countries. my country's fastener products are exported to many countries in the world, and fastener products from all over the world are also pouring into the Chinese market. Fasteners, as one of the products with the largest import and export volume in my country, are in line with international standards, which have important practical significance and practical significance for promoting Chinese fastener enterprises to go to the world and promoting fastener enterprises to fully participate in international cooperation and competition. strategic significance. Due to the specifications, dimensions, tolerances, weights, properties, surface conditions, marking methods, and specific requirements of items such as acceptance inspection, marking and packaging for each specific fastener product.
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