What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The maximum unscrewing torque of the lock nut is affected by many factors. For the research on the low-cycle fatigue performance of the lock nut, the pitch diameter of the thread, the helix angle and the bevel angle of the thread remain unchanged. Only the maximum elastic restoring force FNmax and the equivalent friction angle ρe of the thread piece will appear to a certain extent after repeated use. Change. Therefore, it is only necessary to analyze the variation law of the maximum unscrewing moment when the lock nut is subjected to cyclic load from these two aspects.
At present, with the development of the manufacturing industry, many parts with strange shapes are widely used in aviation, aerospace and other industrial fields, one of which is an L-shaped cylindrical pin. The upper end is provided with a 2.55×4.95 U-shaped boss. The parallelism error between the upper end face and the lower end face of the boss is required to be less than 0.01 mm. The L-shaped cylindrical pin requires high machining accuracy and is difficult to clamp on the machine tool. It is difficult to process. When the forming part is cut off, the cut surface, that is, the upper end surface of the boss, will leave a small column platform. When processing this end surface, in the prior art, a vise is generally used to process such an L-shaped cylindrical pin. Or copper sleeves are clamped, and then processed; however, due to the small size of the parts, the L-shaped cylindrical pin workpiece is difficult to clamp; due to the high precision required for each machined surface of the workpiece, when clamping with a vise , the clamping force of the vise is difficult to control, and it is easy to crush and scratch the surface of the workpiece; and when using a vise or a copper set clamp, only one workpiece can be clamped for each processing and production, and it is difficult to ensure the upper and lower planes of the parts after the clamping is completed. Parallelism machining error, resulting in low parts processing quality and low production efficiency.
1. When the main body is large-scale equipment, accessories need to be installed, such as sight glass, mechanical seal seat, deceleration frame, etc. The stud bolts used at this time, one end is screwed into the main body, and the other end is equipped with nuts after the accessories are installed. , Since the accessories are often disassembled, when the main body and the accessories are directly connected by bolts, the main body threads will be worn or damaged over time, and it is very convenient to use studs to replace them. 2. When the thickness of the connecting body is very large and the bolt length is very long, stud bolts will be used. The purpose of anti-loosening of stud connection In actual work, the external load has vibration, change, high temperature creep of the material, etc., which will reduce the friction force, the positive pressure in the thread pair disappears at a certain moment, and the friction force is zero, thus making the threaded connection loose. , if repeated action, the threaded connection will loosen and fail. Therefore, it is necessary to prevent loosening, otherwise it will affect the normal work and cause accidents.
Flat gaskets are usually thin pieces of various shapes used to reduce friction, prevent leakage, isolate, prevent loosening, or distribute pressure. There are such components in many materials and structures. The existing flat washer has a simple structure design. After long-term use, the phenomenon of thinning of the thickness is likely to occur, which in turn leads to poor wear resistance of the flat washer.
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