What are the key points for preventing loosening of fasteners such as nuts and bolts?

How to prevent loosening of fasteners? Here are some key points to prevent loosening:

Bolt friction and anti loosening.

This is a widely used anti loosening method that generates a positive pressure between the threaded pairs that does not change with external forces, in order to generate a frictional force that can prevent the relative rotation of the threaded pairs. This positive pressure can be achieved by compressing the threaded pair axially or simultaneously in both directions. For example, elastic washers, double nuts, self-locking nuts, and nylon insert locking nuts are used.

This anti loosening method is more convenient for nut disassembly, but in situations of impact, vibration, and variable load, the bolt will initially experience a decrease in pre tightening force due to relaxation. As the number of vibrations increases, the lost pre-tightening force will slowly increase, ultimately leading to nut loosening and thread connection failure.

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Mechanical anti loosening of bolts

It directly restricts the relative rotation of the threaded pair using a stopper. For example, using split pins, serial steel wires, and stop washers. Due to the lack of pre tightening force on the stopper, the anti-loosening stopper only works when the nut is loosened to the stop position. Therefore, this method is actually not anti loosening but anti falling.

Bolt riveting and anti loosening

After tightening, methods such as punching, welding, and bonding are used to make the thread lose its motion characteristics and become an inseparable connection. The disadvantage of this method is that the bolt rod can only be used once, and disassembly is difficult, and it can only be disassembled if the bolt pair is damaged.

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The bolt structure prevents loosening.

It utilizes the structure of the threaded pair itself, which is Tang's thread-locking method. The first three types of anti loosening methods mainly rely on third-party force for anti loosening, mainly referring to friction, and the effectiveness of their anti loosening depends on the size of the third-party force. And structural anti loosening does not rely on third-party forces, only relies on its own structure. The structural anti loosening method, also known as the Tang's thread anti loosening method, is currently the most effective anti loosening method, but it is not well-known to most people.