Self Locking Nuts
Self-Locking Nut with their internal thread form the counterpart of a screw and ensure that the attached screw does not come loose. Lock nuts (also known as prevailing torque nuts or stiff nuts) are resistant to vibration & torque. Nuts are designed to wear faster than bolts. For self-locking nuts, it is acceptable to reuse them as long as there is still some locking action. The number of components is also reduced by the self-locking feature of the nut since no further securing elements are needed.
Lock nuts feature a unique design that prevents them from loosening when exposed to vibrations. Because the nut insert hole is smaller than the bolt it creates so much friction between all of the threads that are in contact that the nut cannot vibrate loose.
Self Locking nuts should be used when the screw joint consists of one or more soft materials. It is difficult to achieve and maintain a high level of clamp load because the soft material deforms due to high surface pressure.