What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Nuts are parts that tightly connect mechanical equipment. Through the inner threads, nuts and bolts of the same specification can be connected together. For example, M4-P0.7 nuts can only be connected with M4-P0.7 series bolts (in the nut). Among them, M4 means the inner diameter of the nut is about 4mm, and 0.7 means that the distance between the two threads is 0.7mm); the same is true for American products, for example, a 1/4-20 nut can only be matched with a 1/4-20 screw ( A 1/4 finger nut has an inner diameter of about 0.25 inches, and 20 fingers have 20 teeth in each inch).
At present, the commonly used shaft retaining rings in the market usually include elastic retaining rings and screw locking retaining rings, but they all require tools to be installed and disassembled, which is relatively inconvenient to use.
Therefore, in order to obtain fasteners that meet the requirements, it is usually necessary to anneal the middle sections of bolts, rivets, etc. to reduce the hardness of the middle sections, while ensuring the hardness of the heads of bolts, rivets, etc. At present, the existing process adopts ultra-high frequency induction heating equipment to instantly heat the middle section and reduce the hardness. However, this process requires a lot of control, and the heating time is slightly longer, which affects the hardness of the head, and the mass production is very unstable, which is easy to cause the rivet to fail. At the same time, the cost of ultra-high frequency equipment is high and the power consumption is large, which is not conducive to mass production and energy saving. Environmental friendly.
At present, the main four kinds of anti-shedding nuts are still prone to falling off. Friction and anti-shedding are in the case of shock, vibration and variable load. At the beginning, the nut will decrease in preload due to relaxation. As the number of vibrations increases, the loss of preload will increase. The force increases slowly, eventually causing the nut to loosen and the threaded connection to fail. The mechanical nut is prevented from falling off by adding a stopper, which makes it inconvenient to disassemble. The riveting and punching prevention is to prevent the separation by welding, bonding, etc. This method can only be disassembled by destroying the bolt pair.
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