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Written by G.L. Huyett Marketing Department on 06/03/2021 with 0 comments

Lock Nuts, Jam Nuts, and Bearing Lock Nuts: What They Are and How They Work

Not all nuts are created equal. There are times when the need arises for a threaded fastener that resists loosening and lock nuts—sometimes written "locknuts" or "locking nuts"—are frequently the go‑to solution.

What is a locknut?

A lock nut is an internally threaded fastener that possesses locking capabilities either by itself or in concert with another component. By design, lock nuts are engineered to resist loosening when subjected to vibration or torque.

What are the different lock nut types?

A wide variety of locking nuts are manufactured for a variety of purposes. We will focus on the most common styles offered by G.L. Huyett. This includes lock nuts with nylon inserts, jam nuts, and bearing lock nuts.

Lock Nuts with Nylon Inserts

Nylon insert lock nuts—also known as nylon nuts and stop nuts—are a prevailing torque, locking nut that resists loosening caused by vibration and normal use. Unlike free spinning hex nuts, lock nuts make use of a deforming elastic or metal material to stay in position against torque and shock. Nylon insert lock nuts are a popular solution for many applications, however they are limited to applications exposed to temperatures under 250°.

Lock Nut with Nylon Inserts

How Do Lock Nuts with Nylon Inserts Work?

Hex lock nuts use a nylon insert at the top of the nut creating tension between the nut and the threads of the mating component. That's why they are sometimes, confusingly, called nylon nuts, but they should not be confused with nuts made entirely of nylon.

As the nut is threaded onto a shaft or rod, it will spin freely until the threads from the host part engage the nylon insert. The threads of the mating shaft will displace the nylon and create resistance. This resistance prevents unintentional moving of the lock nut. The nylon in traditional hex lock nuts can wear, and become less effective after repeated removal and installation. For optimum holding power, replace the nut if it needs to be removed during disassembly of a component.

How to Install a Lock Nut with Nylon Inserts

Prevailing torque lock nuts are installed with the locking end of the nut positioned so that it engages the mating threads. When installing, the nut should thread on freely until the mating threads of the host component engage the nylon insert.

Lock Nut

Jam Nuts

Jam nuts, or half nuts, are a low‑profile hex nut with a profile half the height of a standard hex nut. Jam nuts are used as a locknut to prevent vibration from loosening a bolted joint. Before nuts were developed with "self‑locking" capabilities, two jam nuts would be tightened against each other so that nuts won't loosen over time.

Jam Nuts

How Do Jam Nuts Work?

Jam nuts use opposing friction against either another jam nut or a standard hex nut to lock into position on a threaded shaft or rod. There are conflicting viewpoints on which nut should be installed first. However, the most common use case involves the jam nut being tightened down first. The jam nut is followed by the second nut which is tightened or "jammed" against the first jam nut.

It is difficult to get both nuts properly torqued in this configuration, thus making it undesirable for critical applications where the assembly carries a tension load.

Jam Nuts Use

Bearing Lock Nuts

Bearing lock nuts, sometimes called shaft locknuts or bearing retaining nuts, are utilized to secure bearings onto a shaft and are designed to prevent the loosening of components due to vibration and rotation. Bearing locknuts possess a different appearance from traditional hex lock nuts. Bearing locknuts are typically rounded on the outside with keyed slots. This design requires a special tool called a spanner wrench or socket to be installed or removed. Bearing locknuts are used in a wide variety of applications, including the automotive and agriculture industries.

Bearing Lock Nut

How Do Bearing Lock Nuts Work?

Bearing lock nuts require a positive locking action, similar to castellated nuts, to lock in place. Bearing lock nuts are mated with bearing lock washers to achieve locking capabilities. The machined grooves in the face of the nut provide a mating surface for the tangs of the lock washer to fold into, locking both components in place.

Bearing Lock Nut Use

Looking for more?

Follow our blog page for more information about lock nuts as well as other products and services from G.L. Huyett, including engineered fasteners, lifting and rigging hardware, wire forming, and many more topics. If you have questions about a product, visit our FAQ pages or give us a call to speak with our friendly, experienced Sales Team!


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