Misuse of fasteners(1)

Update:10 Jun 2019
Summary:

When selecting and using fasteners, we first choose fro […]

When selecting and using fasteners, we first choose from national standards or international standards, and then choose them in the industry or well-known enterprise standards. When necessary, we design and process them as needed. Among the items, anti-loose and fracture prevention are two main considerations.
1, in the coarse and fine
The important couplings on the machine, such as the drive shaft, the flying shaft, etc., the bolts use fine thread. However, when repairing missing parts, some people will replace them with coarse bolts. Due to the large inner diameter of the fine bolt and the small pitch and outer angle, it has the advantages of high strength and good self-locking performance. It has strong ability to withstand impact, vibration and exchange load. After being replaced by coarse bolts, it is easy to loosen or remove. Broken, causing a mechanical accident.
2, pores do not match
Bolts (such as drive shaft bolts, flywheel bolts, etc.) that are subjected to lateral loads and shear forces on the machine. They are mated with the bolt holes. The assembly should be robust and able to withstand lateral forces. Some people do not pay attention to the inspection during assembly. When there is a large gap between the bolt and the bolt hole, the installation is still performed, and as a result, the bolt is loose or broken.
3, thickened nuts
Some people often mistakenly believe that the thickened 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 ring, and the more likely the coupling is Loose.