What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Many standoffs are used in sheet metal and aluminum profile processing. However, the existing pressure riveting nut column generally adopts a clearance fit between the pressure riveting and the pressed plate, which has no effect on the general pressure riveting, but it has high surface quality requirements for aluminum profiles, especially Painting aluminum profiles will have a certain impact. First, because the bottom holes of pressure riveting on aluminum profiles are generally processed on ordinary punching machines, a tapered hole with a horn will be generated, which will further increase the gap between the pressure riveting nut columns. Make the mutual tightening force smaller, causing some aluminum profile components to loosen the riveting nut when installing screws, resulting in unqualified surface quality. Therefore, we urgently need a way to reduce the matching gap with the bottom hole of the aluminum profile pressure riveting. The pressure riveting standoff is used to increase the wrapping force between the pressure riveting standoff and the aluminum profile hole.
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.
Ordinary thread Ordinary coarse thread: Feature code M+ Nominal diameter + Rotation + thread tolerance zone code (pitch diameter, top diameter) - Rotation length Ordinary fine thread: Feature code M+ Nominal diameter * thread pitch + direction of rotation + thread tolerance With code (middle diameter, top diameter) - the length of screwing is omitted for right-handed threads, and the left-handed thread is represented by LH. M 16-5g6g means coarse thread ordinary thread, nominal diameter 16, right-handed, the thread tolerance zone is 5g in the middle diameter and 6g in the major diameter, and the screwing length is considered as the medium length. M16×1 LH-6G means fine thread ordinary thread, nominal diameter 16, pitch 1, left-handed, thread tolerance zone medium diameter and major diameter are both 6G, and the screwing length is considered as medium length. The labeling format is: feature code (cylindrical pipe thread is represented by G, conical pipe thread is represented by NPT) + size code + tolerance grade code + rotation direction G1A--LH represents inch non-threaded sealing pipe thread, size code 1in, left-handed, tolerance The grade is A grade. Rcl/2 means inch thread seal taper pipe thread, size code 1/2in, right-handed.
1. The expansion phenomenon of the spring washer is generally not the problem of the spring washer itself. 2. The spring washer with the expansion ring must be subjected to a radial external tension. The external tension is derived from the tightening axial force generated by the tightening torque. The chamfer creates a radial component of the axial clamping force, which expands the opening of the spring washer. The smaller the chamfer diameter, the greater the possibility of ring expansion. 4. Adding a flat washer between the nut and the spring washer helps to slow down or prevent the expansion of the ring, but the flat washer is too thin or too soft. Prevent ring expansion 5. The reason for the hydrogen embrittlement fracture of spring washers is generally due to unreasonable heat treatment process and the failure of hydrogen removal treatment after electro-galvanizing. A large number of tests and long-term practical experience have confirmed the above analysis.
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