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12 super classic bolt locking designs

2020-09-11

There are three commonly used locking methods: friction locking, mechanical locking and permanent locking. Mechanical locking and friction locking are called detachable locking, while permanent locking is called non detachable locking. Common permanent locking methods include spot welding, riveting, bonding, etc. this method mostly destroys threaded fasteners during disassembly and cannot be reused. Common friction locking are: using gasket, self-locking nut and double nut, etc. Common mechanical locking methods: use cotter pin, stop gasket and string steel wire rope.

Today, let's share 12 more popular or more popular anti loosening designs on the Internet, one better than the other. I hope these designs can provide you with choices or help.

1. Double nut

Principle of counter top locknut: two friction surfaces are generated during double nut locking. The first friction surface is between the nut and the fastener, and the second friction surface is between the nut and the nut. During installation, the preload of the first friction surface is 80% of that of the second friction surface. Under the action of impact and vibration loads, the friction of the first friction surface will decrease and disappear, but at the same time, the first nut will be compressed, resulting in the further increase of the friction of the second friction surface. The first friction force and the second friction force must be overcome when the nut is loosened. As the first friction force decreases, the second friction force will increase. In this way, the anti loosening effect will be better.

Down thread locking principle: down thread fasteners are also locked with double nuts, but the rotation direction of the two nuts is opposite. Under the action of impact and vibration loads, the friction of the first friction surface will decrease and disappear,

The first nut (right-hand rotation in the figure) will have a loosening trend, that is, the nut rotates to the left. However, the rotation direction of the second nut (left-hand rotation in the figure) is opposite to that of the first nut, so the loosening force of the first nut is directly converted into the tightening force of the second nut. In this way, the nut will never loosen.

2. 30 ° wedge thread locking technology

There is a 30 degree wedge-shaped inclined plane at the tooth bottom of the 30 ° wedge-shaped female thread. When the bolts and nuts are tightened with each other, the tooth tip of the bolt is firmly against the wedge-shaped inclined plane of the female thread, resulting in a great locking force.

Due to the change of the angle of the tooth shape, the normal force generated by the contact between the threads forms an angle of 60 degrees with the bolt axis, rather than 30 degrees like ordinary threads. Obviously, the normal pressure of 30 ° wedge thread is much greater than the fastening pressure. Therefore, the anti loosening friction is bound to increase greatly.

As can be seen from the figure below, the force represented by the two arrows is p ɑ， The normal pressure of traditional 60 degree angle thread is p = 1.15p ɑ； The angle and size of normal pressure of 30 ° wedge thread change because there is a wedge inclined plane with an angle of 30 ° at the tooth bottom, and the normal pressure P = 2p ɑ。

In this way, the ratio of normal pressure between 30 ° wedge thread and traditional 60 ° thread is ≈ 12 ∶ 7, and the anti loosening friction increases accordingly. The wedge-shaped surface of 30 ° wedge-shaped thread can also eliminate the problems of uneven stress and tripping seizure of ordinary thread.

3. Self locking nut

Self locking nuts are generally self-locking by friction. The 30 ° wedge thread locking mentioned above should belong to the category of self-locking nuts.

It is divided into: high-strength self-locking nuts for road construction machinery, mining machinery and vibration machinery equipment, nylon self-locking nuts for aerospace, aviation, tank and mining machinery, swimming self-locking nuts for products with working pressure not greater than 2atm, working medium of gasoline, kerosene, water or air and service temperature of - 50 ~ 100 ℃, and spring clip self-locking nuts.

4. Thread locking compound
Thread locking adhesive is an adhesive composed of (meth) acrylate, initiator, promoter, stabilizer (polymerization inhibitor), dye and filler in a certain proportion.