Double nut structure is a classic anti-loosening fastening solution

The double nut structure is a classic anti-loosening fastening solution that resists loosening under vibration and dynamic loads through the interaction of two nuts (such as friction, deformation or mechanical interlocking). In recent years, with the improvement of reliability requirements in industrial equipment, rail transportation, aerospace and other fields, the development of double nut structures has made significant progress in materials, design optimization and intelligent monitoring. The following is the current status and trend of its technical development:

1. Double nut anti-loosening principle
Friction anti-loosening:

The upper nut (locking nut) applies additional preload to increase the friction of the thread contact surface.

The lower nut (main nut) bears the main load, and the two form a bidirectional friction resistance.

Mechanical interlocking:

Deformed nut: The upper nut uses nylon inserts (such as Nyloc) or metal deformed teeth to bite the thread.

Wedge effect: For example, Hardlock nuts produce a wedging effect through an eccentric structure.