Spex Logo

Different Types of Lock Nuts

Different Types of Lock Nuts

Lock nuts are a special part that’s designed to hold parts and assemblies together. These parts are built to be used for long periods of time.

Spex machines different types of precision lock nuts for various industries and uses. Today we’ll share some info about how lock nuts are manufactured and used.

What are Lock Nuts?

A lock nut is a type of nut that’s designed to not loosen over time. There are different methods to keep the nut secure, including adhesive, pins, and features that increase friction. Some lock nuts are designed for single use, making them less effective or unusable after they’re removed.

In general, nuts are used for assemblies that need to be disassembled. That’s helpful when different parts need to be cleaned or to perform regular maintenance. Lock nuts are more difficult to assemble and disassemble, but they provide greater security and reduce the risk of parts coming loose. 

Lock nuts are commonly used for assemblies where there are moving parts or vibration, which causes other nuts to loosen over time.

How do lock nuts work?

There are a few different ways that a lock nut stays secure. The three common ways are adhesive, friction, and pins.


The most common type of lock nut has some type of adhesive. This could be a type of glue, or a nylon ring that creates a tight seal on the bolt. 


Some lock nuts have specific features that increase the friction. Some have grooves on the bottom of the nut, which increases friction with the surface that the lock nut is touching. Other lock nuts have specific threading that increases the friction between the nut and bolt. Both of these designs make it more difficult for the nut to come loose.


Lock nuts that use pins have a hole or groove cut into them. Once the nut is tightened onto the bolt, a pin is inserted through a hole in the nut and bolt to prevent it from spinning off. A cotter pin can also be added on top of a lock nut with grooves cut in the top.

5 Different Types of Lock Nuts

5 Different Types of Lock Nuts

1. Nylon insert lock nuts

These lock nuts have a nylon ring or patch on the inside threading of the nut. When they’re threaded onto the bolt, the nylon creates a seal. These nuts are subject to high temperatures which could melt the nylon, and they require more torque to assemble. 

2. Hex jam nuts

Jam nuts are actually two nuts that are used on top of each other. The second nut is jammed on top of the first one, preventing it from spinning off the bolt. 

3. Center lock nut

A center lock nut has a hold drilled into the center of it. Once the nut is tightened, a punch is used to distort the threading on the bolt, which prevents the nut from loosening. 

4. Serrated Flange lock nut

The serrated lock nut has grooves on the back side of the nut. These nuts are usually used against sheet metal. The grooves on the back of the nut rub against the surface and prevent it from backing out.

5. Castellated nut

A castellated nut has grooves on the top, which look similar to the top of a castle. These lock nuts are used with a bolt that has a hole drilled in it. Then, a pin is inserted through the top of the nut and bolt to secure it in place.

What are lock nuts made of?

Because most lock nuts are used for heavy-duty and industrial applications where strength is a priority, most are made with stainless steel or mild steel. Stainless steel alloys are the most common material because it’s strong and resistant to corrosion. Zinc and brass locking nuts are also fairly common. 

In cases that require less strength, nylon or plastic lock nuts are popular because they’re less expensive to manufacture and lightweight.

Spex is an ISO 9001:2015 certified precision machine shop in Rochester, NY. We machine thousands of unique metal and polycarbonate parts every month for different industries around the world. Reach out to our team to see if we can help with your next project. 

Related content

Contact us

Fill out the form to learn more about our precision machining services.

We would love to hear from you! Please fill out this form and we will get in touch with you shortly.

  • Max. file size: 256 MB.
  • This field is for validation purposes and should be left unchanged.
Spex Logo

Phone: (585) 467-0520

Email: sales@spex1.com

85 Excel Drive
Rochester, NY 14621