UNC & UNF Nyloc Nuts for Secure Fastening

Bremick Imperial Nylon Nuts provide a practical locking solution for imperial threaded assemblies where vibration or movement could contribute to an ordinary nut working loose. Also known as imperial nyloc nuts, nylon insert lock nuts, UNC nyloc nuts & UNF nyloc nuts, they use an integrated nylon insert to create resistance against the mating thread.

They're suited to machinery, agricultural equipment, automotive repairs, fabrication, workshop maintenance & existing imperial assemblies where the correct fractional size, thread pitch & nut specification matter.

Replacing the mating fastener at the same time? Browse Hex Bolts. For the broader range of locking nuts, compare Nylon Insert Nut.

Buying tip: if you have the old bolt or nut in your hand, don't order from the fractional diameter alone. Identify the diameter, count or gauge the threads per inch, confirm UNC or UNF & check the required grade or finish. Those four checks eliminate most avoidable mismatches.

What Are Imperial Nylon Nuts?

Imperial nylon nuts are hexagonal lock nuts with an integrated nylon collar near the top of the nut.

As the correct bolt or stud passes through the metal thread & reaches the nylon section, the insert conforms around the male thread. This creates prevailing resistance that helps the nut resist unwanted rotation.

Depending on the application, you'll also see them described as:

► Imperial nyloc nuts
► Nylon insert lock nuts
► UNC nyloc nuts
► UNF nyloc nuts
► Imperial lock nuts
► Self-locking nuts
► Nylon locking nuts
► High tensile nyloc nuts
► Zinc plated nyloc nuts
► Stainless steel nyloc nuts

The nylon insert provides the locking action, but the metal thread still needs to match the bolt correctly.

For alternative locking-nut configurations without the same nylon insert arrangement, browse Lock Nut.

Why Choose Bremick Imperial Nylon Nuts?

Built-In Resistance to Unwanted Nut Movement

The locking feature is incorporated into the nut itself.

Once the mating thread reaches the nylon collar, additional resistance is created around the bolt thread. This makes nylon insert nuts useful for specified connections exposed to vibration, movement or repeated equipment operation.

The nut still needs to be correctly selected & tightened for the assembly. The nylon insert doesn't compensate for incorrect thread engagement, damaged hardware or unsuitable joint design.

UNC & UNF Options for Imperial Fasteners

Imperial thread identification deserves more attention than simply measuring the outside diameter.

A fastener might be:

► 1/4" UNC
► 1/4" UNF
► 3/8" UNC
► 3/8" UNF
► 1/2" UNC
► 1/2" UNF
► 5/8" UNC
► 5/8" UNF

The nominal diameter can be identical while the threads per inch differ considerably.

That's why UNC nyloc nuts & UNF nyloc nuts need to remain clearly separated in workshop stock.

Practical for Existing Imperial Machinery

Fractional fasteners remain common across older machinery, imported equipment, agricultural hardware, trailers, mechanical assemblies & workshop-built equipment.

If you're replacing an existing imperial nylon lock nut, keep the original mating bolt or stud until you've confirmed:

► Diameter
► Threads per inch
► UNC or UNF
► Nut grade where applicable
► Material
► Finish

That original hardware can tell you much more than an unlabelled nut sitting in a parts tray.

Common Applications

Machinery & Plant Maintenance

Nylon insert lock nuts are regularly used on specified machinery connections where unwanted nut rotation needs to be resisted.

During maintenance, don't inspect only the nut.

Check the mating bolt or stud for:

► Flattened threads
► Burrs
► Corrosion
► Cross-threading
► Damaged thread starts
► Paint or coating build-up
► Dirt & contamination

Installing a new nyloc nut onto damaged male threads doesn't repair the underlying problem.

Agricultural Equipment

Agricultural machinery can accumulate decades of replacement hardware.

That makes thread identification particularly important.

A tractor, implement, pump or trailer can contain different imperial thread systems depending on its manufacturer, age & repair history.

Never assume every fractional fastener is UNC.

Automotive & Mechanical Repairs

Imperial nyloc nuts can be encountered on older vehicles, trailers, imported machinery & mechanical equipment.

Keeping removed hardware organised by assembly makes replacement easier.

A loose 1/2" nut tells you relatively little. A 1/2" nut kept with its original bolt gives you the opportunity to identify both diameter & thread pitch.

Fabrication & Workshop Assembly

Workshop stock becomes much easier to use when imperial lock nuts are labelled by thread rather than diameter alone.

Instead of:

1/2" Nyloc Nuts

use:

1/2"-13 UNC | Nylon Insert Lock Nut

or:

1/2"-20 UNF | Nylon Insert Lock Nut

That immediately distinguishes coarse & fine threads.

Equipment Mounting

Brackets, guards, accessories & equipment components can use nylon locking nuts where specified.

For critical, highly loaded or safety-related connections, follow the required fastener specification rather than substituting locking methods simply because another nut fits the thread.

Product Selection Guide

Buying Bremick Imperial Nylon Nuts? Check These 5 Things First

If you're ready to choose a product from the collection, work through these checks in order:

Imperial diameter

Identify the nominal fractional size, such as 1/4", 3/8", 1/2" or 5/8".

UNC or UNF

Don't stop once the diameter matches. Determine whether you need a coarse UNC thread or finer UNF thread.

Threads per inch

Use the TPI to confirm the thread. For example, 1/2"-13 is UNC while 1/2"-20 is UNF.

Grade, material & finish

Check whether the assembly calls for a particular mechanical grade, zinc plated steel, stainless steel or another specified option.

Application

Confirm that a nylon insert locking nut is actually appropriate for the connection, particularly where temperature, critical loading or specialised operating conditions are involved.

If all five details agree with the product specification, you've got a much stronger basis for choosing the right nut.

Quick UNC vs UNF Buying Guide

Already know the bolt diameter? Use the thread count to narrow down the nut.

TPI means threads per inch.

For example:

1/2" diameter + 13 TPI = 1/2"-13 UNC

1/2" diameter + 20 TPI = 1/2"-20 UNF

If you know only that you have a 1/2" bolt, you don't yet have enough information to order the nut confidently.

Which Imperial Nyloc Nut Should I Buy?

Use this as a quick decision guide:

The most important buying rule is simple: match the complete fastener specification rather than choosing the nut that looks closest.

Choosing UNC Nyloc Nuts

UNC uses a coarse Unified thread.

Common imperial UNC nylon nut sizes include:

► 1/4"-20 UNC nyloc nuts
► 5/16"-18 UNC nyloc nuts
► 3/8"-16 UNC nyloc nuts
► 7/16"-14 UNC nyloc nuts
► 1/2"-13 UNC nyloc nuts
► 5/8"-11 UNC nyloc nuts
► 3/4"-10 UNC nyloc nuts

If your existing bolt is clearly identified as 1/2"-13 UNC, select a 1/2"-13 UNC nylon insert nut with the appropriate grade, material & finish.

Don't order a 1/2"-20 UNF nut simply because both are labelled 1/2".

Choosing UNF Nyloc Nuts

UNF uses a finer Unified thread.

Common sizes include:

► 1/4"-28 UNF nyloc nuts
► 5/16"-24 UNF nyloc nuts
► 3/8"-24 UNF nyloc nuts
► 7/16"-20 UNF nyloc nuts
► 1/2"-20 UNF nyloc nuts
► 5/8"-18 UNF nyloc nuts
► 3/4"-16 UNF nyloc nuts

If the equipment specification calls for a fine thread, make sure the product description confirms UNF & the correct TPI.

A nut that appears to start onto the bolt isn't enough evidence that the threads match.

Replacing an Existing Nyloc Nut

Have the old hardware?

Use it.

Before buying a replacement:

► Keep the original bolt & nut together
► Read any markings on the hardware
► Measure the bolt diameter
► Gauge or count the TPI
► Determine UNC or UNF
► Check the nut grade where required
► Identify the material & finish
► Inspect the bolt for damage

If the original nut was used in a specified locking arrangement, replace it with the appropriate locking-nut type rather than automatically changing to a standard hex nut.

Buying for Workshop Stock

Stocking imperial nylon nuts is different from buying one replacement fastener.

For workshop inventory, prioritise the thread sizes actually used across your machinery, vehicles & equipment rather than filling bins with random fractional sizes.

Label each bin with:

Diameter | TPI | UNC/UNF | Nut Type | Grade | Finish

For example:

3/8"-16 | UNC | Nylon Insert Lock Nut | Zinc

This makes repeat purchasing easier & reduces the chance of mixing coarse & fine threads.

Buying for an Older Machine With No Fastener Specification

Don't guess from the age or country of manufacture.

Remove an accessible example where appropriate & identify the actual thread.

Older equipment can contain original hardware, previous repairs & later substitutions in the same machine.

If the existing fastener can't be confidently identified, measure it before ordering replacement nuts.

Nyloc Nut vs Standard Hex Nut

Both can have the same thread size, but they don't perform the same job.

A standard hex nut doesn't contain the integrated nylon locking collar found in a nyloc nut.

A nylon insert lock nut adds prevailing resistance within the nut.

Which one belongs in the connection depends on the assembly specification.

For conventional imperial nut requirements, browse Hex Nut.

Imperial Nyloc Nuts vs Metric Nyloc Nuts

Put an imperial & metric nylon nut beside each other & the difference may not be obvious.

Internally, they're different thread systems.

If your existing bolt is imperial, buy an imperial nut with the matching thread.

Don't substitute an M-size nut because the diameter appears close.

Zinc Plated or Stainless?

Material & finish should come after you've established the correct thread.

If both options are available in the required size, consider:

► Existing bolt material & finish
► Environmental exposure
► Required mechanical properties
► Equipment specification
► Connected materials
► Service conditions

Stainless isn't automatically an upgrade for every connection.

Match the requirements of the assembly.

What About Grade 8 Nyloc Nuts?

Higher-strength imperial nylon insert nuts are available for applications requiring them.

Grade is separate from thread size.

A 1/2"-13 UNC Grade 8 nyloc nut can have exactly the same nominal thread as another 1/2"-13 UNC nut while being intended for different mechanical requirements.

If you're mating the nut with high-strength imperial hardware, confirm the specified nut grade rather than choosing by fit alone.

Start the Nut by Hand Before Reaching for a Tool

This is one of the easiest checks you can perform after buying.

Clean, compatible metal threads should begin engaging smoothly by hand before the bolt reaches the nylon insert.

Immediate binding can indicate:

► Wrong diameter
► UNC/UNF mismatch
► Damaged bolt thread
► Damaged nut thread
► Corrosion
► Contamination
► Coating build-up

Don't use extra leverage to make an incorrect thread fit.

Know When the Nylon Insert Has Engaged

Once the bolt reaches the nylon locking section, additional turning resistance is expected.

That's different from incompatible metal threads fighting each other from the first turn.

If you're unsure, compare where the bolt is sitting relative to the nylon collar before continuing.

Can Imperial Nyloc Nuts Be Reused?

Don't automatically assume a previously installed nylon lock nut will provide the same locking characteristics indefinitely.

Suitability for reuse depends on the condition of the nut, application & requirements governing the assembly.

Where reliable locking performance matters, follow the relevant equipment, engineering or maintenance specification.

Consider Temperature Before Buying

The locking element is polymer.

That makes operating conditions relevant.

Where the connection is exposed to elevated temperatures, aggressive chemicals or specialised service conditions, confirm that a nylon insert locking nut is appropriate before ordering.

Another locking method may be required for some environments.

Don't Forget the Rest of the Connection

Replacing the nut is a good opportunity to inspect the complete assembly.

Check the:

► Bolt or stud
► Washer
► Connected surfaces
► Threads
► Existing locking arrangement

For conventional load-spreading requirements, browse Flat Washer.

For the wider fastening range, browse Bolts & Fasteners.

Expert Tips

Take the old bolt to the parts bench. It's much easier to match an imperial nylon nut when you have the mating thread available.

Know the diameter but not the TPI? Don't order yet. That missing measurement can be the difference between UNC & UNF.

Separate UNC & UNF workshop stock. Fractional diameter alone doesn't identify an imperial thread.

Add TPI to workshop labels. “3/8"-16 UNC” is far more useful than “3/8 nuts”.

Don't identify thread size from the spanner. The hex size tells you which tool fits the nut, not which internal thread it contains.

Buying several sizes for one machine? Check each connection. Don't assume one piece of equipment uses the same thread series everywhere.

Start clean fasteners by hand. Incorrect metal threads shouldn't require a socket to get started.

Expect additional resistance when the nylon engages. Resistance from the first turn deserves investigation.

Inspect the mating bolt. New locking hardware won't repair damaged male threads.

Check grade independently of thread. A nut can fit the bolt while still being unsuitable for the specified connection.

Consider operating temperature. Nylon locking inserts aren't the answer for every environment.

For a practical overview of thread matching & common fastening families, read Fastener Guide Bolts Screws Anchors.

Small components can have a significant effect on equipment reliability. Why Good Fasteners Matter More Than the Tool You Drive Them With looks more closely at why correct fastening hardware matters.

For a maintenance perspective from equipment operating in demanding conditions, read Quarry Crews Crusher Maintenance.