Tension indicator

A one-piece mechanical device for visually indicating if the tension in a monitored bolt is below, is within and is above a predetermined range, said device comprising a substantially helical spring washer for insertion inbetween the head of the monitored bolt and the bearing surface against which the head of the monitored bolt exerts a force, said washer having opposed bearing surfaces and having ree ends which are opposed but axially spaced apart when the washer is in an uncompressed state, said washer of a spring constant such that compressive forces equal to less than the predetermined range of tensile forces in the monitored bolt will cause only minimal axial compression, compressive forces equal to tensile forces within the predetermined range will cause substantial but not total resilient axial compression and complete axial compression of the washer will occur only upon the application of a compressive force equal to greater than the predetermined range of tensile forces in the monitored bolt;

• said washer having an axially extending outer circumferential wall of substantially constant axial length, said outer circumferential wall of greater axial length than the remainder of the washer, the free ends of the washer each carrying indicia markings on the outer circumferential wall thereof, said indicia markings being spaced from and substantially centrally located between said opposed bearing surfaces and axially aligning only when the washer axially compresses under a compressive force equal to tensile forces within the predetermined range.