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 of each circle, and the easier it is to loosen the coupling.

2. Improper locking

Important bolts should be locked with anti-loosening device after assembly. When using a split pin to lock, the common mistake is to use a thin split lock or a half-split lock to lock; when using a spring washer to lock, the common mistake is that the gap of the washer opening is too small and loses elasticity; using a lock plate to lock Yes, the common mistake is to lock the lock plate at the corners of the nut; the double nut is used to lock, the common mistake is to install the thinner nut on the outside and not tighten it tightly.

3. false and solid

There are impurities such as rust stains, scale, iron filings, sand particles in the threads of bolts, nuts or screw holes, or there are impurities such as burrs and sand on the joint surface of the coupling parts, which have not been removed before assembly. When tightening the bolts, due to impurities Blocking effect, the surface is tightened very tightly, the torque value meets the requirements, but in fact the coupling is not really compressed; in addition, there is another situation, due to the supporting effect of sludge, scale and other impurities in the screw hole, Although the bolt torque complies with the regulations, the work piece is not tightened. Under such false solidity, vibration, load shock and temperature changes often cause the bolts to loosen quickly.

4. one female with multiple pads

During installation, sometimes the bolts after assembly are too long, so someone installs many spring washers on one bolt. In this way, the spring washers are not evenly stressed during the tightening process, and some will break, which will pre-tighten the bolts. The force drops; or eccentric load is generated, which reduces the reliability of the bolt connection.