What is a locking nut?

A locking nut, also known as a locknut or a prevailing torque nut, is a type of fastening device used to secure threaded fasteners such as bolts or screws. Its primary function is to prevent loosening or backlash caused by vibration or other external forces.

Locking nuts are commonly used in various industries, including automotive, aerospace, machinery, and construction, where maintaining the integrity of fasteners is crucial for safety and performance.

There are different types of locking nuts available, each designed to suit specific applications and requirements:

  1. Nylon Insert Locknuts: These nuts feature a nylon ring insert that provides friction resistance against loosening. When tightened, the nylon compresses and creates a prevailing torque, keeping the nut locked in place. These nuts are reusable but may lose their effectiveness over time due to wear.

  2. Metal Locknuts: Metal locknuts, also known as prevailing torque locknuts, use a metal insert or deformable threads to achieve locking functionality. These nuts have a higher resistance to heat and vibration compared to nylon insert nuts, making them suitable for more demanding applications.

  3. Center Lock Nuts: Center lock nuts are designed with a built-in washer that prevents rotation and loosening of the nut. The washer provides additional surface contact, distributing the load more evenly and reducing the chances of self-loosening.

  4. Serrated Flange Nuts: Serrated flange nuts have serrated edges on the flange, which bite into the surface of the material when tightened. This creates resistance against rotation and prevents loosening. They are commonly used in applications where the nut is exposed to excessive vibration.

  5. Stover Nuts: Stover nuts are one-piece, all-metal locknuts that feature rounded corners on the top surface. These rounded corners increase the prevailing torque, providing resistance against loosening caused by vibration. Stover nuts are commonly used in automotive applications.

Using a locking nut ensures that the fastener remains securely fastened, reducing the need for frequent inspections and tightening, and preventing potential hazards caused by loose connections. However, it is essential to choose the right type of locking nut based on the specific application requirements to ensure optimal performance.