Got a application that calls for top-notch vibration resistance? Looking to secure critical components without worrying about loosening over time? Locking nuts with nylon inserts may be just what you need! These ingenious fasteners provide unparalleled locking ability thanks to their unique design.

In this article, we’ll break down everything you need to know about locking nuts with nylon inserts. We’ll cover how they work, their key benefits, and how to choose the right one for your project. Let’s dive in!

The Ins and Outs of Locking Nuts with Nylon Inserts

How Locking Nuts with Nylon Work

Locking nuts contain a nylon insert that presses against the threads of the mating bolt to prevent loosening. Here’s a quick rundown of how they do their job:

This unique locking action remains effective even under demanding applications with vibration, temperature changes, or frequent disassembly/reassembly.

Key Benefits of Locking Nuts with Nylon Inserts

There are several reasons why locking nuts with nylon inserts are a go-to solution for critical fastening needs:

Excellent Resistance to Vibration Loosening

The nylon insert applies constant pressure to the bolt threads, preventing loosening from vibration better than any other nut. This makes them ideal for equipment like engines, pumps, and heavy machinery.

Reusable Locking Ability

The nylon insert can be reused multiple times without losing its locking effectiveness. Standard lock nuts and washers can wear out over time.

Withstand Temperature Fluctuations

The nylon insert maintains its integrity whether operating temperatures fluctuate, expand, or contract. This ensures a solid hold in hot or cold conditions.

Quick Visual Inspection

It’s easy to see if a locking nut is properly installed – the nylon should be slightly visible protruding from the nut’s end. No special tools needed!

Compatible With Many Thread Sizes/Types

Locking nuts with inserts are available in metric and inch sizes and fit standard thread types like UNC, UNF, etc.

Choosing the Right Locking Nut with Nylon Insert

To select the optimal locking nut for your application, there are a few key factors to consider:

Nut Strength/Grade

Locking nut strength is indicated by grades like Grade 5, Grade 8, etc. Match this to the strength of the mating bolt. Using a nut with equal or slightly higher strength prevents the bolt from failing first.

Nut Style

Common options include hex, jam, and flange nuts. Make sure the nut style properly fits the assembly and allows for easy installation.

Nut Height/Width

The locking nut’s dimensions must allow it to fit within the space allotted in the assembly. Measure bolt length and housing thicknesses to ensure proper fit.

Temperature Resistance

If the application sees very high or low temps, choose a nut with an insert material that can withstand the extremes. Nylon has an operating temp range of -40°F to +392°F.

Corrosion Resistance

Stainless steel locking nuts resist corrosion in water, chemicals, etc. If corrosion is a concern, don’t use plain carbon steel nuts.

Locking Nut Options to Consider

Now let’s look at some of the most common types of locking nuts with nylon inserts to consider for your application:

Hex Nuts

Hex nuts are the simplest, most universally used locking nut. Their hexagonal shape allows for easy wrenching with standard tools. Grade 8 hex nuts provide excellent strength for critical applications.

Flange Nuts

Flange nuts feature a large bearing surface that distributes force over a wider area. This prevents damage to softer materials. The flange also makes them easier to hold in place during tightening.

Jam Nuts

Jam nuts are two nuts tightened together on a threaded rod to “jam” against each other. This creates excellent resistance to vibration loosening. Use jam nuts to secure threaded rods in structural assemblies.

Non-Metallic Nuts

For extreme corrosion resistance, choose nuts made of plastic materials like nylon or PTFE. These stand up to harsh chemicals and ocean environments. Just be aware of their lower strength limits.

Stainless Steel Nuts

Stainless provides top-level corrosion protection while maintaining good strength. Common grades are 304 and 316 stainless. The nylon insert gives these nuts the added benefit of vibration resistance.

Proper Installation of Locking Nuts

To get the full benefit of your locking nuts with nylon inserts, proper installation is critical. Here are some tips:

  • Clean the nut threads and bolt to remove dirt, oil, etc. Debris can reduce locking effectiveness.
  • Hand tighten the nut until snug. The nylon should slightly extrude from the outer end.
  • Tighten to the bolt manufacturer’s spec using properly calibrated torque wrenches. Don’t over-tighten!
  • For jam nuts, tighten both nuts together against each other.
  • Visually inspect that the nylon is protruding from the nut end face after final tightening.

Following these simple guidelines ensures your locking nuts achieve their maximum holding ability. Periodically check installed nuts for proper torque and nylon visibility.

Frequently Asked Questions

What’s the difference between a nylon insert nut and a nylon lock nut?

Nylon insert nuts have the nylon molded into the nut’s threaded hole. Nylon lock nuts have a nylon collar around the outside that presses against the mating part. The nylon insert provides better resistance to loosening.

How many times can you reuse a nylon insert nut?

Properly installed nylon insert nuts can typically be reused 10-20 times before losing effectiveness. This depends on the quality of the insert material and proper installation.

Can I use locking nuts with nylon inserts on stainless steel bolts?

Yes, stainless steel bolts are compatible with nuts containing nylon inserts. The inserts create vibration resistance while the stainless resists corrosion.

What temperature range can nylon inserts handle?

Most nylon insert materials maintain their integrity in temperatures from -40°F to +392°F. Specialty insert materials can handle even greater extremes.

How do I know if a nut and bolt are properly torqued?

Use a calibrated torque wrench to tighten nuts/bolts to the manufacturer’s torque spec. Visually check that the nylon insert is extruded from the nut’s end face after tightening.


With their unmatched resistance to loosening, reusability, and durability, it’s easy to see why locking nuts with nylon inserts are a staple in critical fastening applications. They offer reliable performance across a wide range of operating conditions. Whether choosing hex, flange, or stainless steel varieties, following the proper installation steps ensures these nuts will keep your equipment secure.

For specialty locking nut needs, companies like Jmet Corp offer custom engineering and manufacturing capabilities. Contact them today to discuss custom solutions for your application!