Acorn Nuts

Acorn nuts are closed-end, hex fasteners designed to cover exposed threaded ends on compatible connections. Maintenance teams, fabricators, and assembly professionals use them to help protect exposed threads and create a cleaner, more finished appearance on threaded assemblies.

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Helpful Buying Guide

Acorn Nut Buying Guide

Acorn nuts combine a wrenchable hex body with an enclosed cap. Use this guide to match the thread size, material option, finish, and hex size represented in this category to a compatible threaded assembly.

Visual Guide

Popular examples in this category

Use Cases

Finish exposed threaded connections

Use acorn nuts where the end of a compatible threaded fastener remains exposed and a capped, finished connection is needed.

How to Choose

Match the thread first

Select an acorn nut with the same thread designation as the threaded fastener, such as 1/4-20, 5/16-18, 3/8-16, 1/2-13, or 5/8-11.

Applications

Support maintenance and assembly work

These acorn nuts are suited to maintenance, fabrication, assembly, and other threaded fastening work where exposed thread ends need coverage.

Additional Info

Consider material, finish, and wrenching size

Available options include stainless steel and steel with a black oxide finish. Confirm the listed hex size can be installed with a compatible wrench or socket.

5Thread sizes represented

Options range from 1/4-20 through 5/8-11.

2Material options

Choose from stainless steel or steel.

2Finish appearances represented

Available options include stainless steel and black oxide finished steel.

5/8–1-1/16 in.Listed hex sizes

Defined hex sizes support use with compatible installation tools.

Comparison Guide

Compare Acorn Nut Options

Use the thread designation to match a compatible fastener, then compare construction, finish, and listed hex size.

Thread sizeConstruction and finishListed hex size
1/4-20Steel, black oxideNot specified
5/16-18Stainless steel5/8 in.
3/8-16Stainless steel3/4 in.
3/8-16Steel, black oxide3/4 in.
1/2-13Steel, black oxide7/8 in.
Planning Guide

Plan the right fit before choosing

Start With Compatibility

Match the acorn nut to the threaded fastener

Thread designation is the primary selection point. Each acorn nut is intended for a corresponding compatible threaded fastener. The category includes 1/4-20, 5/16-18, 3/8-16, 1/2-13, and 5/8-11 options.

  • Choose 1/4-20 for compatible 1/4-20 threaded fasteners.
  • Choose 5/16-18 for compatible 5/16-18 threaded fasteners.
  • Choose 3/8-16, 1/2-13, or 5/8-11 to match the corresponding threaded connection.
Compare Construction

Select the listed material and appearance

The available products include stainless steel acorn nuts as well as steel acorn nuts with a black oxide finish. Stainless steel options are offered in 3/8-16 and 5/16-18 thread sizes, while black oxide steel options are represented across several thread sizes.

  • Stainless steel options are available for 3/8-16 and 5/16-18 connections.
  • Black oxide steel options are available for 1/4-20, 3/8-16, 1/2-13, and 5/8-11 connections.
  • Use the listed finish when a black oxide finished appearance is required.
Plan Installation

Verify the hex size for your installation tool

The hex provides the wrenching surface used for installation and removal. Confirm the listed hex size and use a compatible wrench or socket for the acorn nut selected.

  • 5/16-18 stainless steel: 5/8 in. hex.
  • 3/8-16 stainless steel and black oxide steel: 3/4 in. hex.
  • 1/2-13 black oxide steel: 7/8 in. hex; 5/8-11 black oxide steel: 1-1/16 in. hex.
FAQ

Common questions before buying

What is an acorn nut used for?

An acorn nut covers the exposed end of a compatible threaded fastener to provide a more finished appearance and help protect exposed threads.

Which thread sizes are available?

The represented options include 1/4-20, 5/16-18, 3/8-16, 1/2-13, and 5/8-11.

Are stainless steel acorn nuts available?

Yes. Stainless steel options are represented in 5/16-18 and 3/8-16 thread sizes.

What tool is used to install an acorn nut?

Use a compatible wrench or socket on the nut's hex wrenching surface. Listed hex sizes vary by option.