Washers are simple fastening components that are paired with bolts and nuts or screws. They are usually a standard part of a fastener assembly, mainly because of their load distribution and surface preservation advantages.

But apart from adding support and security to joined parts and materials, what else can a washer do? The fact is that flat washers serve many purposes beyond standard spacing and load distribution devices. Their capabilities are vast—and depending on their shape and material—they can be used to perform many functions and solve a series of common problems, a few of which are detailed below.

Sealing

One of the most well-known uses of washers that are not exclusive to load distribution is their use for sealing. Some washers can function almost as well as gaskets in some applications. They can help seal off openings by creating a more flush and uniform connection, whereas a fastener assembly lacking a washer will have an inevitable gap. Even those washers made from standard metal, such as SAE flat washers and USS flat washers, can function in a capacity that limits the flow of air and liquids, but to gain an air or water-tight seal, there are special washers that function in this way.

Sealing washers are often made from flexible, non-absorbent materials like silicone, neoprene, and rubber. They are very similar to gaskets and o-rings. There are also metal flat washers that are designed to be compressed to create a permanent seal. These are sometimes called crush washers.

Electrical And Thermal Insulation

In the same way that washers can be used to contain the flow of liquids and gases, they can also be used to isolate components from the flow of electricity and the transfer of heat. This will require a washer that’s made of a material that’s either electrically or thermally non-conductive. To isolate the flow of electricity, rubber, phenolic, fiber, and plastic flat washers can be effective. To keep fasteners and connections isolated from heat, flat washers made from silicone or neoprene are effective options.

Vibrating Damping And Anti-Slip

Flat washers that are properly tensioned in place will provide reliable stability and prevent assemblies from loosening and vibrating over time. For exceptional vibration damping or anti-slip functionality, a flat washer made from a compressible, cushioning material, especially one with a high frictional coefficient is an effective choice. These materials will provide a grip that prevents components from turning and will also serve as a buffer to eliminate rattling, thus preserving the integrity of the structure or equipment.    

Anti-Tampering

Most fastener assemblies are meant to allow for tightening and loosening for purposes of maintenance and adjustment. However, this arrangement does not suit all applications; in some situations, an assembly must not be held permanently or semi-permanently, or in a way that will not permit any type of tampering. Flat washers with a toothed inner diameter can suit such purposes. These are also sometimes called lock washers because they lock or bite onto the shank of a fastener. Once installed, they cannot be loosened by simply turning the nut. Instead, the assembly cannot be removed unless the washer is cut or stretched using pliers. This makes them a simple but effective anti-tampering measure. In some cases, they are used for safety purposes, such as on children’s toys, to prevent small parts from loosening and posing a safety hazard.

Material Isolation

In some applications, it may be necessary to join components of mixed materials. Problems can arise when these materials are incompatible and the potential for galvanic corrosion increases. A washer is a small but effective option for preventing such reactions. Plastic washers or zinc flat washers can serve as a buffer between incompatible materials, which prevents the formation of rust and other types of material deterioration.