A locking nut, also known as a lock nut, works by resisting loosening under vibrations and torque. There are several designs, but the most common involve either a nylon insert or an all-metal deformed thread that creates friction.
Types of Locking Nuts and How They Work
Here's a breakdown of how different types of locking nuts achieve this:
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Nylon Insert Lock Nuts (Nyloc Nuts): These nuts have a nylon ring inserted at the end. As the nut is tightened, the bolt threads cut into the nylon, creating a tight friction fit. The nylon insert acts as a wedge, increasing the friction between the nut and bolt threads and preventing loosening. However, the nylon insert melts at temperatures higher than 200 degrees Fahrenheit, which limits its use.
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All-Metal Lock Nuts (e.g., Stover Nuts, Prevailing Torque Nuts): These nuts are designed with a deformed thread section. This deformation can be achieved through various methods, such as an elliptical thread or a series of indentations. When the nut is tightened onto a bolt, the deformed threads create friction and gripping force that resist loosening. These are suitable for high-temperature applications where nylon inserts would fail.
Mechanism of Action: Friction and Resistance
The core principle behind a locking nut is increasing friction. Both nylon insert and all-metal lock nuts increase the friction between the nut and the bolt, making it more difficult for vibrations or torque to loosen the connection. This increased friction creates a "prevailing torque" that must be overcome to loosen the nut.
Applications
Locking nuts are widely used in applications where vibration or movement can cause regular nuts to loosen, such as:
- Automotive industry (e.g., suspension components, exhaust systems)
- Aerospace industry
- Machinery and equipment
- Construction
