Abstract: A clamping force monitoring device is provided having a step washer, a contact plate, a compression washer separating the step washer and the contact plate, a threaded fastener extending through the step washer and the compression washer, a nut and an electric circuit, wherein when a sufficient axial force is exerted in the threaded fastener by engagement of the nut, the compression washer is compressed and the step washer is in contact with the contact plate, thereby closing the electric circuit. A method for monitoring a threaded fastener is provided including extending a threaded fastener through a step washer and a compression washer and engaging the threaded fastener with a nut, wherein when a sufficient axial force is applied to the threaded fastener by the nut, the compression washer is compressed and the step washer contacts a contact plate, thereby closing an electric circuit.

Abstract: A clamping force monitoring device is provided having a step washer, a contact plate, a compression washer separating the step washer and the contact plate, a threaded fastener extending through the step washer and the compression washer, a nut and an electric circuit, wherein when a sufficient axial force is exerted in the threaded fastener by engagement of the nut, the compression washer is compressed and the step washer is in contact with the contact plate, thereby closing the electric circuit. A method for monitoring a threaded fastener is provided including extending a threaded fastener through a step washer and a compression washer and engaging the threaded fastener with a nut, wherein when a sufficient axial force is applied to the threaded fastener by the nut, the compression washer is compressed and the step washer contacts a contact plate, thereby closing an electric circuit.

Abstract: The threaded fastener has a head end, a far end and a hollow core between the head end and the far end. A reference rod is mounted inside the hollow core. The reference rod has an anchor end attached to the far end of the threaded fastener and a free end extending in the head end. A flexible contact element is attached to the free end of the reference rod and is movable in the head end of the threaded fastener along a displacement path upon elongation and relaxation of the threaded fastener. Switch elements are mounted in the head end of the threaded fastener along the aforesaid displacement path of the flexible contact element. The switch elements are making calibrated contact with the flexible contact element upon a movement of the flexible contact element during a movement of the flexible contact element along its displacement path.