Toothed Lock Washer

A toothed lock washer, also known as a star washer, has teeth or prongs which extend radially inward and/or outward. This maintains tension and opposes any loosening influence on the fastener. The flexed teeth absorb shock, vibration and slipping. Internal tooth washers have the teeth pointing inward. They are used when the finished appearance requires that the teeth be hidden under the head of the screw, or to avoid the teeth scratching or snagging. Also used with screws with smaller heads. External tooth washers have teeth pointing radially outward. They are used when finished appearance is less crucial as it provides the greatest torsional resistance and therefore locking efficiency because the teeth are on the largest radius.