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Shoulder washers explained

clock 4.5 minutes | 27 May 2022

Black shoulder washers for electric and heat insulation

What are shoulder washers?

A shoulder washer is used to insulate fasteners, wires or shafts from moisture and electricity.

It looks like a typical flat washer on one end with an attached sleeve, or bushing, at the other end. The flange created by this design is inserted into a housing to provide a bearing surface for rotary applications. The flange can also locate the bushing during installation.

Shoulder washer diagram

This guide is designed to answer your questions about this unique washer, covering these topics:


It has many names you should become familiar with to prevent confusion:

  • Bush washers or bushing washer
  • Step washers
  • Shoulder bushing or shoulder bushes
  • Shouldered washers
  • Sleeve washers
  • Insulation washers

Bushing vs. washer

You’ve heard these as two separate words, but what exactly is the difference? Both are essentially hollow cylinders. Bushings are a type of bearing that insulates both moving and stationary parts. You’ll usually find bushings used as a casing for a shaft, hinge or pin or in electrical applications, as an opening for a conductor to pass through.

A washer is a flat disk installed underneath a nut that distributes pressure. A shoulder washer gives you both a washer and a bushing.

Where insulating shoulder washers are used

Wherever electrics are involved, you’re likely to find a shoulder washer in use. You should avoid using them in humid environments. Most industries rely on them, including:

  • Electronic equipment
  • Automotive
  • White goods
  • Construction
  • HVACs
  • Electrical
  • Fabrication
  • Manufacturing
  • Furniture
  • Vending & ATMs

Types of shoulder washers

Below are the different styles of shoulder washers and their uses.

Ideal for white goods

Components exposed to high temperatures, such as found in consumer appliances, can benefit from this washer:

​High-temperature shoulder washer

High-temperature shoulder washer

  • Electrical insulating washers for screws
  • Glass-filled polyphenylene sulfide (PPS)
  • Operating temperature range: -40˚F to 428˚F
  • UL94 V-0

Ideal for PCBs

These washers act as an electrical insulator by preventing metal-to-metal contact:

​Bushing shoulder washer

Bushing shoulder washer

  • Bushing washer type
  • Suitable for light-load bearings or bushing
  • Protective barrier around fasteners to minimize corrosion
  • Reduces vibration
  • Low-friction coefficient
  • Can be used as a locator, sleeve, liner or glide
  • Nylon 6/6
  • Operating temperature range: -40˚F to 185˚F
​Shoulder washer

Shoulder washer

  • Bushing washer type
  • Can also be used as light load bearings due to material’s low coefficient of friction
  • Strong and corrosion resistant
  • Nylon 6/6
​Standard shoulder washer

Standard shoulder washer

  • Standard washer type
  • Lightweight
  • Resistant to corrosion and abrasion
  • High dielectric strength
  • Nylon 6/6
  • Operating temperature range: -40˚F to 185˚F
  • UL94 V-2
​Shoulder washers

Shoulder washers

  • Standard washer type
  • Lightweight
  • Resistant to corrosion and abrasion
  • High dielectric strength
  • Can be used as glides, bumpers, feet or spacers
  • Nylon 6/6
  • Operating temperature range: -40˚F to 185˚F
  • UL94 V-2

Plastic shoulder washers: dielectric strength

A plastic shoulder washer can rightly be called an electrical insulating sleeve washer. A nylon shoulder washer, for example, has outstanding resistance to not only abrasion and most chemicals, but also high voltages. This is why nylon is often used in electro-mechanical components.

Most plastics are poor conductors of electricity, resisting a current flow. This is dielectrics, and why plastics do such an outstanding job as insulators. Plastics are common materials for wire coatings, cables, switches and other electrical applications.

When voltage is applied and increased, the electrical properties of plastics begin to break down, which lowers their resistance.

A material’s dielectric strength tells us its ability to store electrical energy. It’s also a measurement of a material’s dielectric breakdown resistance under an applied voltage. Dielectric strength is expressed as volts per unit thickness and tells you how effective the material is as an insulator.

The higher the value, the more electrically insulating a material is. These plastics all have excellent dielectric strength:

Dielectric strengths

Plastic

Dielectric strength (v/mm)

Nylon 6.6

300-400

Polysulfone (PSU)

425

Polyphenylene sulfide (PPS)

450

30% Glass-filled nylon

530

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 for most solutions to make sure you’ve chosen exactly what you need. If you’re not quite sure which shoulder washers 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.

Washers for PCB