Common misunderstandings in the use of standard bolts

Editor:Jiaxing UNITEK Machinery Technology Co., Ltd. │ Release Time:2021-11-10 

Substituting coarse for fine

Because the fine-tooth standard parts occupy a small space, have the advantages of high strength, good self-locking performance, and strong ability to withstand vibration and exchange loads, the anti-loosening effect is better than that of coarse teeth without taking preventive measures. However, in some mechanical maintenance processes, coarse teeth will be used instead of fine teeth. The consequence is that after using coarse teeth instead, it is easy to loosen, fall off, and break, causing mechanical accidents.

Pore mismatch

The fit of the bolt holes on the machine is a transition fit, and the assembly should be strong and reliable, and able to withstand lateral forces. If the holes are not matched and still installed, the bolts will loose or cut off accidents.

Thicken nut

Thickening the nut can increase the number of working turns of the thread, thereby improving the reliability of the standard parts. However, the thicker the nut, the more uneven the load distribution between the threads of each turn, which is more likely to cause loosening.

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.

Washer is too large

Sometimes, due to the lack of suitable gaskets, some people use gaskets with larger inner diameters instead. In this way, the contact area under the head of the bolt with the washer is small, the bearing pressure or locking force of the washer is reduced, and the bolt is easy to loosen under the action of vibration and impact load.

Torque does not match

Many people think that bolts should be "tighter than loose", so they consciously increase the tightening torque of the bolts, which results in slipping bolts. On the other hand, for important bolts that need to be tightened with torque, some people try to save trouble with adjustable wrenches. Unscrew, the result is often loose due to insufficient torque, leading to mechanical failure.