Patent ID: 8418569

Claim:
A variable torque-rate test joint for the performance testing of rotary tools for threaded fasteners, comprising: a screw-threaded bolt received in a screw-threaded recess in a test rig, for angular displacement by a rotary tool under test; and a torque-rate adjustment device between a head of the bolt and a shoulder adjacent the screw-threaded recess, wherein the torque-rate adjustment device comprises: a washer portion encircling the bolt beneath the bolt head; at least one spring beam extending from a reaction point which is located radially outwardly of the bolt and over a pivot point, to support in cantilever the washer portion; and means for varying the distance between the or each pivot point and a central rotary axis of the bolt, to vary the spring constant exerted by the or each spring beam on the bolt head and thus to vary the effective torque-rate of the test joint.