The Difference between Plain and Spring Washers

Washer components are common hardware pieces, typically coming in the form of a thin plate that has a hole in the middle. When paired with a threaded fastener such as a bolt or nut, the washer serves to distribute loads for the benefit of an assembly. Beyond such a role, washers may also operate as a spacer, wear pad, locking device, preload indicating device, or vibration reducer. Washers may be constructed from various materials such as metal and plastic, and they come in numerous forms to facilitate the operations of different systems. Plain and spring washers are two common variations, each of which differ from one another to benefit varying needs. In this blog, we will discuss the differences between each so that you may better understand the roles that they play.

Plain washers are the most common variation, often being referred to as flat washers due to their design. Generally, such components come in the form of a flat, thin metal plate that contains a hole in the center. To be paired with a threaded fastener, the fastener may be passed through the hole of the washer before being inserted into an assembly. Then, the fastener may be installed into the assembly while having its load amply distributed by the washer. Despite having varying sizes and materials, plain washers are exclusively constructed as a flat piece. While aluminum is commonly used for plain washers, such components may also be made from either carbon steel or stainless steel.

Unlike the flat construction of plain washers, spring washers feature a curved shape. Their curve may be constructed to varying degrees, all of which ensure that the component does not sit flush against a surface during resting conditions. Rather, they can rest flush once a load is exerted on them. Capable of distributing the load of fasteners, spring washers are most beneficial for assemblies that face vibrations. Vibrations are often detrimental to fastened assemblies, posing the risk of components becoming loose over time. To prevent fasteners from coming apart, spring washers may be implemented and will secure the assembly through the use of an axial load.

There are numerous types of spring washers that one may use, those of which include cupped spring, wave, curved disc, split, and tooth locked types. The split washer is a common component, featuring a split at one point that allows for the washer to have a helical shape. With this shape, the washer exerts force between the head of the fastener and the installation material, increasing friction for the means of mitigating rotation. In the instance that a more robust split washer is required, such components are often manufactured to various ASME and NASM standards. Toothed lock washers are another common spring washer variation, featuring serrations that either extend inward or outward from the outer ring. Biting into a bearing surface, the toothed lock washer may act as a lock washer when paired with softer substrates.

1. mark bogart
2. Posted on September 14, 2021
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