What Is the Difference Between Self-Locking Nuts and Lock Nuts?

1. Difference in Working Principles

Self-Locking Nuts

They mainly rely on special structures processed on the threads (such as knurled teeth, deformed threads) to generate additional friction when the nut is tightened, thereby preventing the nut from loosening.

For example, washer-type self-locking nuts achieve automatic locking by compressing elastic washers;
End-face flat self-locking nuts enhance the fastening force through special processing on the nut’s spiral surface.

Lock Nuts

Their anti-loosening principles include embedding serrated washers inside the nut, adding plastic rings outside, or applying special engineering plastic coatings. These structures provide additional fastening force when the nut is tightened.

A typical example: Some lock nuts have special engineering plastics permanently attached to the threads. When the internal and external threads are tightened, the engineering plastic is squeezed to generate a strong reaction force, increasing the friction between the internal and external threads.

2. Difference in Features

Self-Locking Nuts

Excellent anti-loosening performance in vibrating environments, ensuring the firmness and stability of connections. They are often used in scenarios with high reliability requirements, such as fasteners for large vehicles like aircraft, automobiles, and trains.
If disassembled correctly, their self-locking performance is generally not damaged, and they have reusability.

Lock Nuts

High fastening force, suitable for environments bearing large loads and vibrations.
Some lock nuts are made of wear-resistant materials, which can extend their service life.
Their installation method is similar to that of traditional nuts, and no special tools are usually required.

3. Difference in Application Scenarios

Self-Locking Nuts

Generally used in environments with strong vibration, or where high firmness and anti-loosening are required. In addition to large vehicles, they also perform well in harsh environments such as high temperature, high pressure, strong acid, and strong alkali.

Lock Nuts

Usually used in scenarios requiring frequent disassembly, such as sports equipment like racing cars, motorcycles, and bicycles. These devices need frequent replacement of parts, and lock nuts are often used to ensure the stability and reliability of connections.

Supplementary Notes on Key Terms

Deformed threads: A special thread structure for self-locking nuts. The thread profile is intentionally deformed (e.g., 局部挤压 narrowing) during processing. When mated with a bolt, the deformed part creates interference fit, generating persistent friction to prevent loosening.
Engineering plastic coating: A common anti-loosening treatment for lock nuts. Materials like nylon or polyethylene are coated on the thread surface. The plastic’s elasticity and deformability fill thread gaps and create resistance, avoiding nut loosening caused by vibration.
Reusability (of self-locking nuts): Unlike one-time-use lock nuts (e.g., nuts with irreversible plastic deformation), self-locking nuts retain their thread structure integrity after proper disassembly, allowing them to be reinstalled multiple times while maintaining anti-loosening performance.

What Is the Difference Between Self-Locking Nuts and Lock Nuts?