Ten Ways To Tighten Bolts

Mechanical equipment in the bolt connection once slack, will cause the bolt to fall off leading to major safety hazards, or bolt relaxation preload drop leading to bolt connection fatigue life greatly shortened. Therefore, in the design to choose the appropriate anti-loosening measures to ensure that the bolt does not come loose in actual use.

Commonly used in the design of anti-loosening measures are as follows:

1. Double nut

Double nut locking is also known as counter nut locking. When the two top nuts are tightened, there is always an interaction pressure between the two top nuts, and any one of the two nuts needs to overcome the friction between the screwed threads in order to rotate. Even if the external load changes, the pressure between the top nuts always exists, so it can play the role of anti-loosening.

The first nut (right-handed in the diagram) will have a tendency to loosen and retreat, i.e. the nut rotates to the left. However, the second nut (left-hand rotation in the picture) rotates in the opposite direction to 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 back.

2. Self-locking nuts

Self-locking nuts generally rely on friction. The principle is through the embossed teeth pressed into the sheet metal pre-positioned holes, generally square pre-positioned holes in the aperture is slightly smaller than the pressure rivet nut. Using the nut is connected to a locking mechanism, which locks the bolt threads when the nut is tightened.

3. Threadlocker

Thread locking adhesive is an adhesive composed of (meth)acrylate, initiator, co-promoter, stabilizer (polymerization inhibitor), dyes and filler, etc. in a certain proportion.

4. Cotter pin

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

5. Slotted nuts

Slotted nuts are used in conjunction with the screw perforated bolts and cotter pins to prevent the bolts from rotating relative to the nuts.

6. Tandem wire anti-loosening

Tandem steel wire is threaded into the bolt head hole, the bolts in series, play a role in mutual restraint. This is a very reliable way to prevent loosening, but disassembly is more troublesome.

7. Pre-tensioning

High-strength bolted joints generally do not need to apply additional anti-loosening measures, because high-strength bolts generally require the application of a relatively large preload, such a large preload so that the nut and the connection between the strong pressure, this pressure will produce a friction torque to prevent the rotation of the nut, so that the nut will not come loose.

8. Stop washers

After the nut is tightened, the single or double lug stop washer is bent to the side of the nut and the connector respectively and tightened, so that the nut can be locked. If two bolts need to double locking, can be used double brake washers, is two nuts brake each other.

9. Spring washers

10. Double stacked self-locking washers

Buy fastener products, find pandafastener, above is about fastener anti-loosening several methods.