10 classic bolt anti-loosening designs, collect them now!

Mar. 05, 2024

Once the bolt connections in mechanical equipment are loose, it will cause the bolts to fall off and cause major safety hazards, or the pretightening force of the loose bolts will be reduced, which will greatly shorten the fatigue life of the bolt connections. Therefore, appropriate anti-loosening measures should be selected in the design to ensure that the bolts do not loosen in actual use.

Commonly used anti-loosening measures in design include the following:

1. Double nut

Double nut anti-loosening is also called counter-nut anti-loosening. When two counter-top nuts are tightened, there is always an interactive pressure between the two counter-nuts. If any one of the two nuts wants to rotate, it needs to overcome the screw thread. friction between them. Even if the external load changes, the pressure between the top nuts always exists, so it can have a relaxing effect.

2. Self-locking nut

Self-locking nuts generally rely on friction. The principle is to press into the preset holes in the sheet metal through embossed teeth. Generally, the diameter of the square preset holes is slightly smaller than that of the rivet nut. Use a nut to connect to the locking mechanism. When the nut is tightened, the locking mechanism locks the bolt thread.

Built-in nylon self-locking nut

Deformed thread lock nut

Wedge and hammer nut in one

Wedge action locknut

3. Thread locking glue

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

4. Cotter pin

After the nut is tightened, insert the cotter pin into the nut groove and the tail hole of the bolt, and open the tail of the cotter pin to prevent the relative rotation of the nut and bolt.

5. Slotted nuts

Slotted nuts are used with threaded hole bolts and cotter pins to prevent the bolt from rotating relative to the nut.

6. Series steel wire to prevent loosening

Series steel wire anti-loosening is to insert the steel wire into the hole in the bolt head and connect the bolts in series to restrain each other. This anti-loosening method is very reliable, but disassembly is troublesome.

7. Preload

High-strength bolt connections generally do not require additional anti-loosening measures, because high-strength bolts generally require a relatively large pre-tightening force. Such a large pre-tightening force creates strong pressure between the nuts and the connected parts. This pressure creates frictional torque that prevents the nut from turning so it doesn't come loose.

8. Stop gasket

After the nut is tightened, bend the single-lug or double-lug stop washer toward the side of the nut and the connecting piece to lock the nut. If two bolts need to be double locked, double brake washers can be used to brake the two nuts against each other.