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A guide to retaining washers

clock 5 minutes | 20 May 2022

Retaining washers used in an automotive engine application

Retaining washers are also known by other names which hint at their purpose: anti-loss washers and retention washers. These are used to keep assemblies in place, typically in industrial and automotive applications.

In this guide, we'll cover:

The purpose of retaining washers

There are two types. One contains two separate, round holes. One hole enables a screw or bolt to affix the washer to the assembly while the other hole is used for attaching a chain, cord or wire to the same assembly. This is a less common type of retaining washer.

Less common retaining washer

More common are retaining washers that have a round hole with internal protrusions. Still others have one round hole with no protrusions, or teeth. Retaining washer types are designed to:

  • Retain screws on an outer panel
  • Prevent screws from falling when unfastened

When the washer is placed over the screw, the internal lugs within the washer grip the male thread. This is especially helpful in the automotive industry, where screws are used upright. For speed of assembly, it’s critical to use a washer that stays in place as the screw is installed.

Many retaining washers are excellent for pre-assembly. This in turn reduces your end assembly cost while saving time. These washers are also used as a temporary mount for fasteners. They’re often thin to minimize the gap they create on a flat panel. The secure hold that retaining washers provide make it ideal for applications when vibration is present.

Retaining ring washers are different still. These are a type of clip retaining washer. They’re designed to fit into pre-manufactured grooves on axles.

Retaining ring washer

This also makes them a type of shaft retaining washer. They act as shoulders to retain a specific component or assembly. In the example here, the lip makes assembly and disassembly easy. Other types of clips require a retaining washer tool for installation and retaining washer removal.

You can learn more about washers and other fasteners in our Ultimate guide to fasteners.

Types of retaining washers

Below are push-on retainer washers that slide over the screw shank. These retaining lock washers are ideal for pre-assembly.

Retaining washer
  • Internal teeth for gripping screw shank
  • Self-retaining washer for quick assembly
  • Natural nylon 6/6
Retaining washer
  • Internal teeth for gripping screw shank
  • Natural nylon 6/6
Retaining washer
  • Inside diameter designed to grip the outside of the screw shank
  • Slides onto the screw easily
  • Ideal for applications requiring pre-assembly of the screw and washer
  • Natural nylon 6/6
Retaining washer
  • Internal teeth for gripping screw shank
  • Natural nylon 6/6
Retaining washer
  • Internal teeth for gripping screw shank
  • Natural nylon 6/6
Retaining washer
  • Easily slides onto screw
  • Internal teeth for gripping screw shank
  • Ideal for pre-assembly
  • LDPE
  • Available in red, blue or gray

What are sealing washers?

You might also need sealing washers, which are designed to create a close-fitting, water-tight seal. They’re often used in plumbing applications or to maintain an ingress-protection rating between cord grips and equipment.

Sealing washer
  • Toothless
  • Self-retaining washer for quick assembly
  • Enables preliminary mounting of the bolt before securing with a nut
  • Tapered design retains the screw prior to assembly
  • Cold forms and fully enters the pitch of the screw to provide sealing
  • Natural nylon 6/6
Sealing washer
  • Toothless
  • Self-retaining washer for quick assembly
  • Natural nylon 6/6

Plastic retaining washers

Metal retaining washers are available, with the most common ones being aluminum and stainless-steel retaining washers. But plastic is becoming the popular choice for multiple reasons:

  • Insulation against moisture and electricity
  • Ease of assembly
  • Absorbs vibration
  • Weather resistance
  • Cost

Plastics are also lightweight, which makes it especially popular with an automotive industry tasked with lowering emissions. They’re also ideal for electric vehicles, which also needs lightweight solutions. Nylon retaining washers are the most common, and for good reason. Nylon resists corrosion, wear and friction, making it suitable for high-wear applications. Another popular plastic is low-density polyethylene (LDPE). Here’s how the two compare:

Nylon 6/6

LDPE

Tensile strength – pull apart (psi)

12,400

1,400

Dielectric strength – insulation (v/mil)

300 – 400

460-700

Bending stiffness (psi)

410,000

30,000

Resistance to chemicals

Dilute acid

Poor

Excellent

Dilute alkalis

Fair

Excellent

Oils & greases

Excellent

Fair (variable)

Aromatic hydrocarbons

Excellent

Poor

Halogenated hydrocarbons

Good (variable)

Poor

Alcohols

Poor

Excellent

Plastic insulation retaining washers are different than retaining washers. These are used in construction and building to secure insulation materials in place. They work in a similar way in that they secure a screw, but their uses are different.

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples to make sure you’ve chosen exactly what you need. If you’re not quite sure which screw retaining washer will work best for your application, our experts are always happy to advise you.

Whatever your requirements, you can depend on fast despatch. Request your free samples or download free CADs now.

Questions?

Email us at sales@essentracomponents.com or speak to one of our experts for further information on the ideal solution for your application 800-847-0486.

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