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Washer (hardware)

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A washer is a thin plate used in mechanical engineering and construction.

Washers.agr
Washers.agr

Most washers are disk-shaped with a central hole. They are typically placed between a threaded fastener, like a bolt or nut, and the surface being fastened. The primary purpose of a washer is to distribute the load of the fastener. This prevents the fastener from crushing or damaging the material underneath.

Plain washer1
Plain washer1

Beyond load distribution, washers serve as spacers, bearings, or locking devices. They can also act as insulators to prevent electrical flow or galvanic corrosion. This corrosion happens when different metals, like steel and aluminum, touch each other.

Plain washers, often called flat washers, are the most common type. They provide a smooth surface to spread pressure evenly.

Plain washer1
Plain washer1

Some versions, known as fender washers, have a very large outer diameter. These are useful for spreading loads on thin sheet metal, such as automobile fenders. In the United Kingdom, these are often called penny washers. Another specialized version is the torque washer. These have a square hole to fit a carriage bolt. The teeth on these washers bite into wood to prevent the bolt from spinning while tightening.

Spring washers use axial flexibility to maintain tension in a joint. A common type is the split washer, which is a ring split at one point. It is bent into a helical shape to create spring force. This force creates friction between the bolt and the nut. This friction helps prevent the fastener from loosening due to vibration.

Bolt, Plain washer and Spring lock washer
Bolt, Plain washer and Spring lock washer

Other spring washers include the Belleville washer. This is a conical, or cup-shaped, washer that provides significant force when compressed.

Belleville washer
Belleville washer

Wave washers are similar but exert less force and have a wavy shape.

Locking washers use physical interference to stop rotation. Toothed lock washers, or star washers, have serrations that bite into the surface.

External tooth lock washer
External tooth lock washer

These are very effective on soft materials like plastic or aluminum. There are four main styles: internal, external, combination, and countersunk. Internal star washers have teeth on the inner edge for a better look. External star washers have teeth on the outer edge for more holding power.

Federringep
Federringep

Combination washers use both edges for maximum grip. These teeth can also provide a conductive path for electrical grounding by cutting through surface paint.

Advanced locking technology includes the wedge lock washer. This is a hardened, two-piece washer with radial teeth.

Wedge Locking Washer
Wedge Locking Washer

The two halves form a wedge seam. This design requires extra tension to separate the parts after they are tightened. This makes them excellent for preventing loosening caused by heavy vibration. Another type is the tab washer. This metal piece has a side tab that a user bends against a nut. This physically blocks the nut from turning around the shaft.

Washers are manufactured from a wide range of materials to suit specific needs. Steel is common, especially hardened steel for high-quality bolted joints. This prevents a phenomenon called brinelling, where the surface is dented under high torque. Non-ferrous metals like copper, brass, and titanium are also used.

Washers.agr
Washers.agr

For electrical insulation, engineers use plastics like nylon or PTFE, also known as Teflon. Phenolic washers are another choice for insulation because they are heat resistant and tough. In plumbing, soft metal washers like copper or aluminum are used as crush washers. These create a seal to prevent liquid or gas leaks in engines and pipes.

While they look similar, washers and gaskets serve different roles. A washer is usually a structural component for a fastener. A gasket is a seal used to prevent leaks in connections like taps or valves. Some people colloquially call these gaskets "washers," but they are designed differently. For example, a Dowty washer uses a central rubber ring to create a high-pressure seal. Understanding these distinctions is vital for maintaining machines and building structures safely.

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🖼️ Images & Media (15)
File:Washers.agr.jpg
Washers.agr.jpg
File:Plain_washer1.jpg
Plain_washer1.jpg
Fender_washer.tif
File:Anchor_2_(PSF).png
Anchor_2_(PSF).png
File:Belleville washer.jpg
Belleville washer.jpg
File:Curved spring washer.jpg
Curved spring washer.jpg
File:Wave washer 22mm-43mm 2016-03-03.jpg
Wave washer 22mm-43mm 2016-03-03.jpg
File:Grower01.jpg
Grower01.jpg
External tooth lock washer.tif
File:Federringep.jpg
Federringep.jpg
File:ARFISA 27.jpg
ARFISA 27.jpg
File:Wedge Locking Washer.jpg
Wedge Locking Washer.jpg

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