The principle of self-locking lies in its unique structure.

As shown in Fig. 1, there is a wedge-shaped slope of 30 ° on the bottom of the female thread. When the bolt and nut are tightened, the cusp of the bolt is tightly pressed against the wedge surface of the self-locking thread, resulting in a large locking force . The normal force generated by the contact between the threads is at an angle of 60 ° to the axis of the bolt due to the change in the angle of the teeth, rather than forming an angle of 30 ° as in the case of ordinary threads. Obviously, the thread normal pressure is far greater than the fastening pressure, so the resulting anti-frictional friction will inevitably greatly increased.

When the bolt tension is also P0, the traditional 60 ° angle of the normal pressure P = 1.15P0,

The self-locking thread due to the bottom of the tooth has a 30 ° angle of the wedge-shaped slope,

The normal pressure of the angle, the size has changed, the normal pressure P = 2P0, the ratio of the normal pressure of about 12: 7 self-locking thread of the anti-frictional friction corresponding increase.

Self-locking thread wedge-shaped surface can also remove the force of the ordinary thread uneven, tripping and other issues off.

Common thread - 60 ° angle V-shaped thread in its first thread engagement surface and the second thread engagement surface bearing 70% to 80% of the load, while the next few meshing surface to bear the load is small. As a result of ordinary threaded fasteners in the work of vibration load conditions, it is easy to overcome the screw on the contact surface of the locking force to produce rotation, and then loose,

This is why ordinary threaded fasteners are loose.

           Figure 1 self-locking nut structure                                 Figure 2 for the ordinary thread and self-locking thread force state.