Plain vs Spring Washers: What’s the Difference?

Bolt mounted with a washer

Consisting of a thin donut-shaped plate of metal with a hole in the center, washers are used to distribute the load of a fastener. Fasteners will create a load when driven into an object. With a washer, this load will be distributed across a large area, thereby protecting the object from damage. While all washers are designed to distribute the load of a fastener, there are available in several types, including plain and spring.

What Is a Plain Washer?

The most common type of washer, a plain washer. Also known as a flat washer, a plain washer features a simple design consisting of a flat and thin plate of metal with a hole in the center. It’s inserted through a threaded fastener. When the fastener is driven into an object, the plain washer will distribute its load.

All plain washers are flat. That’s essentially what defines them. Some plain washers are made of aluminum, whereas others are made of carbon steel or stainless steel. Plain washers are also available in different sizes. Regardless, they are all flat. A washer is considered a plain washer if it’s flat.

What Is a Spring Washer?

A spring washer, on the other hand, is a type of washer that featured a curved shape. Unlike plain washers, they aren’t flat. Spring washers are curved. They can curve in different ways, but all spring washers feature a curved shape that prevents them from resting flush against a surface without the presence of a load.

Spring washers allow for the distribution of faster’s load as well, but they are particularly useful for applications involving vibrations. Vibrations can cause fasteners to loosen. If a fastener is driven into a machine or object that vibrates, it may loosen to the point where it comes out. Spring washers prevent this from happening. They provide an axial load that will secure the fastener in the object.

Some of the different types of spring washers include the following:

  • Cupped spring
  • Wave
  • Curved disc
  • Split
  • Tooth locked

Difference Between Plain and Spring Washers

Plain and spring washers are both used to distribute the load of a fastener. The difference lies in their shape. Plain washers are flat, whereas spring washers are curved. For most applications, plain washers are typically used. For machines and objects that vibrate, spring washers are recommended. Spring washers are unique because they provide an axial load that counters vibrations and, thus, prevents fasteners from loosening.

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