Fan Disc washers have serrations that extend radially inward or outward to bite into the bearing surface and they are especially useful as a lock washer when used with a soft substrate, they are very similar to shake proof washers and have the same purpose.
This lock washer when used with a soft substrate, such as aluminum or plastic, can resist rotation more as compared to a plain washer on hard surfaces and are especially effective as a lock washer when used with a soft substrate, as the tension between washer and the surface is applied only over a much smaller area (the teeth). There are four types: internal, external, combination, and countersunk. The internal style has the serrations along the inner edge of the washer, which makes them more aesthetically pleasing. Since these washers have serrations around the outer edge hence they provide better holding power, because of the greater circumference. This style which has serrations about both edges, for maximum holding power is a good combination. The countersunk style is designed to be used with flat-head screws.
Tooth lock washers are also used for ground bonding where a metal lug or object must be electrically bonded to a surface. The teeth of the washer cut through surface oxides, paints or other finishes and provide a gas-tight conductive path. In these applications, the washer is not placed under the head of the screw (or under the nut), it is placed between the surfaces to be bonded. In such applications, the fan disc washer does not provide any anti-rotation locking features.
Bhalla Auto Manufacturing Co. is producing a wide range of Fan disc and star washers including in stainless steel and carbon alloy steel material.