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What is a Washer Used For?

What Is A Washer?

A washer is a thin plate, often manufactured from metal, but frequently manufactured from plastic, rubber, fibre, or other materials. Washers come in many shapes and sizes, and can be circular, square, curved, angled, or flat. A washer always contains a hole, which is commonly circular, but can be any shape. A washer does not have a singular purpose, and is a very common addition to many forms of fastening, that is used for a wide variety of reasons.

Top 4 Reasons For Using A Washer

Threaded fasteners are more reliable when used in conjunction with washers for a number of reasons. The main benefits of using a washer in your connection assembly include:

  • It spreads out the load evenly. By distributing the pressure, it ensures a more predictable level of stress.
  • It can protect the surface from damage.
  • Helps to prevent threaded fasteners from moving.
  • Helps to protect from corrosion and therefore increases product life expectancy. 

What Are The Types Of Stainless Steel Washers (And What Are They Used For)?

Washers for Load Distribution

The primary purpose of a washer is usually load distribution. In this case, a washer essentially acts as an extension of the screw head, causing greater distribution of force on the surface of the material being fastened into. Without washers, screws are more likely to dig into surfaces, potentially causing damage and even structural weaknesses if overtightened.

Washers for Preloading

Preload is a form of tension which acts upon a fastener after installation, it is a force which pushes upwards and downwards after a screw is tightened. Preload is most easily represented by a nut and bolt, where the nut pushes in one direction, and the head of the bolt pushes in the other.

Preload is important for several reasons. Most importantly, maintaining tension will prevent loosening under vibration or loosening under the expansion caused by temperature changes.

Preload occurs in all fasteners as they are tightened, but a washer with elastic properties, such as a spring washer or wave washer, can be used to increase the preload acting upon a fastening.

Washers for Aesthetics

A washer can also serve as protection for soft or easily-damaged housings. The use of a washer puts a barrier between the fastener and the surface. with fasteners with non-cylindrical heads such as hexagon bolts, which can leave visible scratches on vulnerable housings. Specialised countersunk washers such as Finishing Washers are designed specifically for their aesthetic appeal.

Washers for Captivation (Captive Washers)

Specialised washers such as captive washers are designed with unconventional functions in mind. A captive washer is held captive on the threads of a screw, locking a screw to a chosen panel, and preventing the screw from being lost if uninstalled. For more information on captive screws and captive washers, see our article What is a Captive Screw?.

Sealing Washers

Specialist Sealing Washers, and washers manufactured from soft material such as rubber, fibre, and even soft metals such as copper, can also be utilised for their sealing properties, making them ideal materials for sealing washers, or as a pre-attached component of sealing screws. Nitrile O-rings and gaskets are also designed to seal the application. By using a softer material, a tighter fit can be created, potentially creating watertight or airtight fastenings. 

Washers for Spacing

Washers are commonly used to create specific height settings for fastenings, and in certain applications, many would consider the terms Spacer and Washer to be interchangeable.

Where ultra-precise spacing is required, specialised Shim Washers or “shims” are used, which are machined to extremely tight tolerances. Shim washers are commonly machined to minute thicknesses of as low as 0.05mm, and can be manufactured even thinner on request.

Locking Washers

Locking Washers are a type of washer typically designed to resist loosening under vibration, but can also be used to hinder tampering. One of the most common types of locking washer is a relatively simple design of angled fins which permit the washer to be rotated in one direction for tightening, but resist movement in the reverse direction.

Accu stocks a range of anti-vibration washers including Nord-Lock Washers which work in pairs to create a wedge locking mechanism. They are used to resist extreme shock and vibration. For more information on locking washers, read our article 6 reasons why bolts become loose and 6 ways to prevent it. 


There is a vast array of applications for washers, from basic load distribution and aesthetics, to more complex specially designed components such as captive washers and locking washers. Whatever your application, you will find the ideal components at