With a grip that's second only to wedge lock, these washers stop nuts and screws from wiggling loose under constant, vigorous vibration. They are ideal for engines, turbines, generators, and other heavy duty equipment. Similar to a spring, they flatten under pressure to add tension between mating surfaces. As long as the washers aren't deformed or otherwise damaged, you can reuse them indefinitely without losing locking strength. Also known as conical washers and Belleville washers.

Stack multiple washers in the same direction to double or triple how much weight they can bear. Stack washers in opposite directions for better deflection, which means they compress further and withstand more shock and movement without loosening.