1. Thickened nut
Some people often mistakenly believe that thickening the nut can increase the number of working turns of the thread, thereby improving the reliability of the coupling. In fact, the thicker the nut, the more uneven the load distribution between the threads, and the easier it is to cause the coupling to loosen.
2. Improper locking
Important bolts should be locked with an anti-loosening device after assembly. When locking with a split pin, the common mistake is to lock with an overly thin split lock or half-piece split lock; for locking with a spring washer, the common mistake is that the washer opening is too small and loses elasticity; locking with a locking plate Yes, the common mistake is to lock the lock plate at the corner of the nut; with double nut locking, the common mistake is to install the thinner nut on the outside and not tighten it tightly.
3. False solidity
There are impurities such as rust stains, scale, iron filings, sand grains in the threads of bolts, nuts or screw holes, or impurities such as burrs, sediment and other impurities on the joint surface of the coupling, which are not removed before assembly. Blocking effect, the surface is tightened very tightly, and the torque value meets the requirements, but in fact the connecting piece is not really compressed; Although the bolt torque is within the specification, the workpiece is not compressed. Under such false firmness, vibrations, load shocks and temperature changes often cause the bolts to loosen quickly.
4.one mother and more pads
During the installation, sometimes the assembled bolts are too long, so some people install many spring washers on one
bolt, so that the spring washers are not evenly stressed during the firming process, and some will break, so that the bolts are pre-tightened. The force decreases; or eccentric load is generated, which reduces the reliability of the bolt connection.