Understanding the Function of a Prevailing Torque Nut
Learn what a prevailing torque nut us and the proper way to use it
Prevailing torque nuts are a type of locknut designed to resist loosening under vibration and torque. Unlike standard nuts that rely solely on thread friction, these fasteners maintain a consistent level of resistance to loosening through various mechanical means, ensuring a more secure fastening. Understanding what a prevailing torque nut is, how it’s used, and the precautions necessary for its application is crucial for ensuring reliability and safety in mechanical assemblies.
What is a Prevailing Torque Nut?
Prevailing torque nuts are specially designed fasteners that provide a reliable locking mechanism to prevent loosening under stress and vibration. They achieve this through several design features, such as:
• Deformed Thread Design— This type of nut relies on an interference fit between the nut threads and the shaft or bolt threads to prevent loosening.
This is a one-time-use prevailing torque-style axle nut. It can’t be reused.
This deformation increases the friction between the nut and bolt, enhancing the locking ability.
These oval-shaped nuts are commonly used on axle shafts, ball joints, strut mounting bolts, suspension components, and steering components. They reduce manufacturer installation costs by eliminating the need for castle nuts, cotter keys, and thread-locking sealants.
• Insert-Based Design— Other styles of nuts use inserts made of materials like nylon or metal. These inserts apply pressure to the mating threads, generating a constant torque that resists loosening.
Notice the nylon insert at the top of the nut. This prevents the nut from loosening.
How to install a prevailing torque nut
The nut will start on the bolt or shaft threads easily until it reaches the deformed threads or the nylon insert. As you continue to apply torque to the nut, you gradually form the oval threads into a circle to match the bolt or shaft. The deformation force is what prevents the nut from loosening.
Cautions and Considerations When Removing or Installing These Fasteners
They are a one-time-use fastener
They can’t be removed and then reinstalled. not designed for repeated use. The locking mechanism can degrade with each application, reducing the nut’s effectiveness. It is crucial to replace these nuts after disassembly to ensure continued reliability.
©, 2017 Rick Muscoplat
Posted on by Rick Muscoplat