Flat vs Dimpled Washers: What’s the Difference?


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When shopping for washers, you may come across flat and dimpled washers. They are two of the most common types of washers. Flat and dimpled washers are both disc-shaped fasteners, and they are both used to distribute the load of a threaded fastener. Flat and dimpled washers, however, feature different designs.

What Are Flat Washers?

Flat washers are characterized by their flat shape. Also known as plain washers, they are typically used in conjunction with a bolt and nut. You can insert a bolt through a flat washer, followed by driving the bolt through a set of parts. After attaching a nut on the opposite side of the parts, the bolt will hold those parts together. The flat washer will simply protect the parts from unintentional damage by distributing the bolt’s load.

What Are Dimpled Washers?

Dimpled washers are characterized by their dimple shape. They are still round — just like flat washers. Rather than being flat, though, dimpled washers are dimpled.

With their dimpled shape, dimpled washers act as spring washers. Spring washers offer axial flexibility to counter vibrations. Normally, when threaded fasteners are exposed to vibrations, they may loosen. Vibrations can cause threaded objects to gradually move out of the parts with which they are used. Dimpled and other types of spring washers prevent this from happening by countering vibrations with a spring-like force.

Differences Between Flat and Dimpled Washers

You can use either flat or dimpled washers to distribute the load of a threaded fastener. The difference lies primarily in their shape. Flat washers are completely flat, whereas dimpled washers are dimpled or cupped.

Because they are shaped differently, dimpled washers offer the added benefit of vibration protection. They will protect the threaded fasteners with which they are used from loosening. As you drive a bolt into a set of objects, the head of the bolt will press against the dimpled washer, thus flattening it out. The now-flattened dimpled washer will then exert a spring-like force to counter vibrations.

When to Use Dimpled Washers

For most fastening applications, flat washers will suffice. They are the single most common type of washer. Flat washers are simple, disc-shaped fasteners that are completely flat. When used in conjunction with a threaded fastener, as well as a nut, they will distribute the fastener’s load.

If you’re planning to use them with machinery, equipment or other parts that vibrate, on the other hand, you may want to use dimpled washers. Only dimpled washers will counter vibrations. They will still distribute the fastener’s load, but dimpled washers will protect against loosening by countering vibrations.

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