Preload Indicating Washer

An item round in shape having a centrally located hole. It consists of two concentric (inner and outer) steel rings, the inner ring is smaller in diameter and higher than the other. These rings are sandwiched between two close tolerance plain washers. As the assembly is tightened, the inner ring takes the load and is deformed until the loose outer ring is bound between the upper and lower plain washers and cannot be moved. The tightened load in the bolt is equal to the load required to compress the inner ring. When the binding of the outer ring occurs and can not be moved, it is a sign that the desired load has been reached.