What is the working principle of the nut

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 will be reduced in dynamic loads. In some important occasions, we will take some anti-loosening measures to ensure the reliability of the nut locking. One of the anti-loose measures is to use a lock nut.
There are also three types of lock nuts:
The first is to use two identical nuts to screw on the same bolt, and add a tightening torque between the two nuts to make the bolt connection reliable.
The second is a special lock nut, which needs to be used together with a lock washer. The special lock nut is not a hexagonal nut, but a middle round nut. There are 3, 4, 6 or 8 gaps on the circumference of the nut (depending on the size of the nut and the product series of the manufacturer). Several notches are not only the focus of the tightening tool, but also the entry point of the locking washer.

The third type is to drill through threaded holes from the outer surface of the nut to the inner thread surface (usually two, distributed at 90 on the outer surface), used to screw in small diameter countersunk screws, the purpose is to thread Apply a centripetal force to prevent the lock nut from loosening. A lock nut with better quality sold on the market is inlaid with a small piece of copper that is consistent with the thread of the lock nut on the inner surface of the nut to prevent the radial jack screw from directly contacting the locked thread and damaging the latter . This kind of lock nut has gradually begun to be applied in the occasion of the shaft end locking of rotating parts, such as the anti-loosening of the bearing at the mounting end of the ball screw.
The second anti-loose method is more reliable than the first, but the structure is relatively complicated. Compared with the first two, the third clock has the characteristics of better anti-loosening effect, simpler and more beautiful structure and smaller axial size.