Washers play an important role in many fastening applications. Consisting of a metal disc with a hole in the center, they are used to distribute the load of a bolt. Washers essentially distribute the load across a larger area — the area of the washer itself — to protect parts from stress-related damage.
You can find washers in different styles, however. While traditional washers have a characteristic disc-like shape, keyed washers have an entirely different shape. How do keyed washers differ from traditional washers exactly?
Extensions
One of the main differences between keyed washers and traditional washers is that the former have extensions. As shown in the photo above, keyed washers have several extensions. These extensions or “tabs” allow them to hold bolts in place. Some keyed washers have inner-facing extensions, whereas others have outer-facing extensions. Regardless, they all have extensions, resulting in a key-like shape.
Locking Mechanism
Keyed washers are classified as locking washers. Like other types of locking washers, they are designed to prevent bolts from loosening. Keyed washers, though, use a different type of locking mechanism than other locking washers. Most other locking washers rely on friction to prevent holts from loosening, but keyed washers use a positive mechanical locking mechanism. The extensions press against the bolt to physically hold it in place without relying on friction.
Installation
Keyed washers require a different installation method than traditional washers. They are both designed to accommodate a bolt or similar threaded fastener in the center. When fastening a set of parts, you can drive the bolt through the center of either washer. If you have a keyed washer, though, you’ll need to bend the extensions so that they press against the bolt.
Rotation
Another way that keyed washers differ from traditional washers involves rotation. Traditional washers can rotate after installation. Vibrations or mechanical stress, for instance, can cause them to spin. Keyed washers are designed specifically to prevent such rotation. Once you’ve engaged the extensions by bending them upward, the keyed washer will remain stationary without spinning.
Thread Protection
You don’t have to worry about keyed washers damaging the bolt’s threads. When lifted, the extensions will press against the bolt without applying friction to the threads. Other types of washers, in comparison, rely on friction, which can damage the bolt’s threads. And once the threads become damaged, the bolt may no longer offer a secure hold.
