Anti-loosening Mechanisms Of Anti-loosening Nuts

There are four most commonly used methods for preventing fastener loosening: friction-based locking, mechanical locking, destructive locking, and chemical bonding.

Among these, friction-based locking is the most widely adopted method due to its simplicity of use, ease of installation, high degree of standardization, and reusability.

 

Principle of Friction-Based Locking

This method achieves a locking effect by maintaining a sufficiently large normal force between the threaded components-a force that remains constant regardless of external loads-thereby generating friction that resists any relative motion between the threads.

Examples include spring washers, self-locking nuts, and nylon-insert locknuts.

 

Mechanical Locking

This method utilizes specific locking elements to directly arrest movement, thereby restricting relative motion between the threaded components. However, because a certain clearance exists between the locking element and the contact surface of the threaded fastener, the connection has already undergone a degree of loosening by the time the locking element engages. Consequently, this method provides virtually no effect in maintaining the initial tightness of the assembly; it serves merely to prevent the fastener from completely detaching.

 

Destructive Locking

In this method, after the fastener has been tightened, techniques such as staking (punching/riveting) or welding are applied to the assembly, rendering the threaded components incapable of rotating loose. While this method offers excellent anti-loosening performance, it suffers from low assembly efficiency and a complete lack of reusability. Consequently, it is rarely employed in large-scale, high-efficiency assembly operations.

 

Chemical Bonding

This method involves the use of anaerobic adhesives-either pre-applied or applied during assembly-to achieve a locking effect. As the threaded components are screwed together, the adhesive capsules (if pre-applied) are crushed, forming a thermosetting plastic material characterized by specific levels of strength and toughness. This material completely fills the clearance within the threaded engagement, thereby restricting the rotational movement of the threads and effectively locking the fastener in place.