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Originally Posted On: Washer Wisdom: Lock Washers (mudgefasteners.com)

Apart from the variety of standard flat washers covered in our last article, the next most common type of washers are lock washers. Lock washers contain mechanisms that prevent bolts and nuts from loosening in the face of torque and vibration, thereby creating their namesake “lock” on the assembly.

Internal Tooth Lock Washers

Internal tooth lock washers feature a series of “teeth” extending inward that “bite” into the bearing surface. The teeth help prevent a bolt head or nut from loosening, but also aid in absorbing shock and vibration.

External Tooth Lock Washers (Star Washers)

External tooth lock washers, sometimes known as star washers, feature teeth on the outside of the washer ring that bite into the bolt or screw head. For these washers to work properly, they should be used with screws and bolts that have larger diameter heads, such as pan head and button head fasteners.

Internal / External Tooth Lock Washers

These types of washers are exactly what they sound like, a combination of internal teeth and external teeth, and are often used in electrical bonding. Internal / external tooth lock washers are helpful when trying to span elongated holes, but can also be used between adjustable pieces of an assembly to help maintain the position of the components after the original tightening.

Wedge Washers

Wedge washers, or beveled washers, have serrations on one bearing face and are used in a pairing. The serrated face of each washer is paired against the serrated face of the other in the pair, causing them to indent into the nut and stopping the possibility of rotation. Wedge lock washers are commonly used in construction equipment, railroad, automotive, solar and wind power applications.

If you have further questions about lock washers, please don’t hesitate to contact us for more information.