The complete guide to washers

In this guide, we cover the necessary information about washers you need to know, such as:

Introduction to Washers
Types of Washers and Their Applications
Understanding Washer Materials and Coatings
Sizing and Dimensions of Washers

Introduction to Washers

A washer is a disk placed underneath a nut, an axle bearing or joint. When to use a washer and when not to really depends on the materials you’re using. But first, let’s address the purpose of washers.

Their purpose is to help threaded fasteners do a more reliable job while protecting the surface from damage during tightening. A perfect example of this is when the material you’re fastening to is weaker than the fastener material itself. Without a washer, the fastener can distort the material it’s being installed into. To prevent this, you need a large bearing surface, which the washer provides.

If the fastener and the material it’s being driven into are the same – for example, metal to metal – then a washer isn’t necessary. That said, certain types of washers can still be advantageous, such as a lock washer, to prevent the fastener and nut from loosening. The bottom line is, it’s smart to always use washers. You can learn more in our guide, How to keep bolts from loosening.

At a glance: purpose of a washer

• Distributes the load of the threaded fastener to prevent damage to the material being fastened
• Prevents fastener from moving or corroding
• Absorbs vibrations
• Can sometimes act as a spacer
• Enhances the lifespan of application

Types of Washers and Their Applications

Not just any washer will do for all applications. Lots of questions surround the application of washers, such as what washer should I use? What goes first, flat washer or lock washer? What are the different washer uses?

For every type of washer, there are subcategories, but here are the three main types you should know about.

1. Plain washers

Their purpose is to distribute the fastener’s load while reducing heat and friction during the tightening process. They can also be used as spacers, as is common in industrial and domestic applications. Different types of plain washers include:

2. Lock washers

The purpose of a lock washer is to prevent the fastener from rotating or losing friction due to vibration or torque. There are many lock-washer types, such as washers with teeth, but they all do this by holding the nut and bolt in place. Some bite into the bolt and the nut with their ends. Lock washers are a favourite in transportation industries such as automotive and aerospace. You’ll also find them in household appliances such as washing machines.

3. Spring washers

What are spring washers for? Some people specify these as a separate category of washers, but they’re actually a type of lock washer. These provide axial load to fasteners to limit movement in case of vibration or thermal expansion. Spring washers are perfect for applications that require a degree of flexibility. All of these reasons are why actuators on airplanes, including the flight controls and landing gear, are examples of spring washer uses.

Understanding Washer Materials and Coatings

Washers are available in metal, rubber and plastic. When high strength is needed, go with a metal washer. Rubber is ideal when flexibility and a tight seal are needed. Plastic is perfect for smaller applications. An example is electronics, which need washers that resist vibrations.

Nylon vs. rubber washers

When you hear of rubber washers, the material is typically nitrile, which is a synthetic rubber. This material and nylon share some of the same properties, especially when it comes to sealing washers. Rubber is softer and more flexible, which enables these washers to provide effective seals to irregular surface areas. A drawback to rubber versus nylon is that rubber distorts quickly under high compression forces. Consequently, it can shorten the life of the washer.

Metal washers

Types of metal washers vary, as do the metals. Stainless steels vary as well, depending on their grade. For instance, some stainless steels are not very corrosion resistant, while others are. You can learn about grades in our guide Understanding stainless-steel grades.

Softer metals, such as copper, can also resist vibration in machines, helping to keep connections secure. Of course, coppers can also be hard if treated. Steel is similar. Low-carbon steel washers are common, as is stronger steel washers.

The chart below is not intended to be the final word on metal characteristics, as so much depends on how the metal has been treated. Still, it’s a good starting point to decide what characteristics you’re after if you’re using metal.

Plastic washer materials

Plastics are more cost effective than metals. If your application doesn’t require high strength, consider using a plastic washer. They’re especially ideal for electronics, when electrical isolation and resistance to vibration is needed. Some are available in colours, but you can also get clear plastic washers. Your choices are vast, from plastic sealing washers to high-density polyethylene washers. Compare the materials below:

1=Poor/ 2=Fair / 3=Good / 4=Very good/ 5=Excellent

Sizing and Dimensions of Washers

Flat washers are the most commonly used washers. The standards here are set by the ISO (the International Organization for Standardization), the worldwide federation of national standards bodies.

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 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.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.