What is the difference between self-locking nuts and locking nuts?

What is a self-locking nut?

A self-locking nut is a nut that secures itself through friction. Conventional nuts may loosen during use due to vibration or other factors. To prevent this, self-locking nuts were developed. Their primary functions are anti-loosening and vibration resistance, making them suitable for specialised applications. They typically operate by friction-based locking. Self-locking nuts are categorised by function into types featuring nylon inserts, flanged necks, or metallic anti-loosening devices. All belong to the category of torque-type anti-loosening nuts.

What is a locking nut?

Locking nuts are widely employed in mechanical and related industries. Their operational principle relies on friction between the nut and bolt for self-locking. However, the reliability of this self-locking mechanism diminishes under dynamic loads. In critical applications, additional anti-loosening measures are implemented to ensure reliable nut locking.

Locking nuts generally fall into two categories: one involves tightening two identical nuts onto the same bolt, applying an additional torque between them to secure the connection; the other comprises specialised anti-loosening nuts requiring use with anti-loosening washers. The specialised anti-loosening nut is not a hex nut but a round nut with six notches cut into its circumference. These notches serve both as grip points for tightening tools and as engagement points for the anti-loosening washer's locking tabs. The second method offers greater reliability than the first but involves a relatively more complex structure.