The Purpose Of Washers & Why They Are Used With Fasteners

Why is it called a Washer?

A washer typically involves a flattened, circular-, or disc-shaped piece of metal with a hole in the middle to allow for a threaded fastener to fit through, such as a bolt or nut.

Nuts and bolts work by applying torque to a threaded shaft, reinforcing the joint and reducing component fatigue; this is especially crucial for variable loads such as machine parts that vibrate.

Washers are also necessary for preventing galvanic corrosion, particularly when protecting steel screws from aluminium surfaces.

High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to brinelling after the torque is applied.

What is the real purpose of washers and why are they used?

Load Distribution

The primary purpose of washers is to reduce the risk of damage and distribute the load of the threaded fastener with which they are used.

Threaded fasteners stress the material that they are driven into. For example, driving a screw into a wooden surface may crack the surface and damage the internal lumbar.

Not all materials require washers, but for wood and other soft materials, it is generally safer to incorporate washers.

Spacing

Washers can also be used as spacers, but why?

It is not possible to drive a threaded fastener if it is longer than the depth of the object, which will leave part of the fastener protruding out the back of the object and possibly damage it.

The correct placement of a washer can easily combat this as it creates padding so that the fastener does not go too deep.

Vibration Absorption

Certain types of washers are designed to absorb vibrations, also known as vibration damping or vibration-isolating washers.

Typically, they are made from a soft material such as plastic, rubber, or urethane, rather than metal.

Softer materials are better equipped to handle vibrations when compared to hard materials like metal.

A vibration damping washer can protect objects that vibrate aggressively, such as within planes or cars.

Liquid Protection

Liquid-sealing washers can be used to create a waterproof seal to prevent seepage water or other liquids. The washer is made from soft materials as this provides better defence when pressed completely against the surface of the object.

Preventing Galvanic Corrosion

Washers can be used to help prevent galvanic corrosion, especially steel screws on aluminium surfaces.

When should you use washers with bolts?

Bolts are more reliable when used with washers. They protect the surface from damage during installation by distributing the pressure to give the nut a smooth, even surface to tighten against, which helps to prevent corrosion and pull-through, especially with softer materials.

Skipping washers can dramatically reduce the lifespan of your product or wherever it is being applied.