If a nut is difficult to install, it is also more difficult to make it fall off. In most cases, this is beyond doubt. However, when using lock nut fasteners, the torque they install more firmly will not offset all the forces that may loosen the fasteners. Once the torque is offset, it is only a matter of time before it falls off.
There are actually many factors that negatively affect the performance of fasteners, such as: bending force, corrosion, hydrogen embrittlement, joint movement, prying force, steep shock load, extreme temperature and vibration. How to control these negative effects has long troubled people. Therefore, lock nuts are used because they are specially designed to prevent bolts from loosening.
It has always been recognized that the way to ensure that the bolt connection provides sufficient safety is to use a combination of two independent nuts: first tighten the thinner nut, and then tighten the thicker nut. However, this method still requires regular inspections and frequent maintenance, because an invisible force has been acting on the fasteners to loosen them during use.
Give an example of fasteners used on railways. Railroad tracks need to constantly resist a large amount of vibrations caused by train operation, while maintaining the integrity of the connecting parts at the same time. Throughout history, the occurrence of railway accidents is often due to the damage of the connecting part, and this kind of damage is caused by the loosening of the fasteners. However, this kind of loosening can be solved with anti-loose technology.
The lock nut is easy to install and can be reused. Precision machinery self-locking nuts with copper pins are widely used in machine tools, engineering and other industries. The working principle of the nut is self-locking by the friction between the nut and the bolt. However, the reliability of this self-locking under dynamic load will be reduced. In some important occasions, we will take some anti-loosening measures to ensure the reliability of the nut locking. The lock nut is one of the anti-loosening measures.
The anti-loosening effect of the lock nut mainly depends on the interaction force between the nut and the bolt engaging thread. There are many ways to improve the interaction force between meshing threads, such as structural improvement of nut threads and surface treatment of threads.
The traditional locking method requires two nuts and washers to be tightened together, but with the vibration of the application body, the two-piece nut and washers will gradually separate, resulting in poor locking effect. The precision lock nut is combined with the threaded copper pin embedded in the nut. When the nut is tightened, it starts to squeeze the copper pellet pin so that the copper pellet pin bites the external thread tightly, effectively preventing loosening and stopping.
