Patent ID: 8261421

Claim:
A method of establishing and checking the axial preload in a tightening portion of at least one shank of the screw or stud type, the method comprising the steps of: providing a shank, a shank gripper member and a tensioner; wherein the shank includes a tightening portion and an extension portion; wherein the tensioner includes a tensioner body and at least three pressing and measurement means; wherein the tensioner body forms a ring; wherein the at least three pressing and measurement means include a cavity, a piston and an optical reader device within each pressing and measurement means; wherein the at least three pressing and measurement means are disposed on an interior side wall of the tensioner body and wherein the at least three pressing and measurement means are spaced equal distances apart around the ring formed by the tensioner body; disposing the tensioner in a rest configuration and bringing the shank gripper member into contact with the tensioner in said rest configuration prior to establishing the preload; tensioning the extension portion of the shank having the tightening portion using the shank gripper member and the tensioner to establish a preload; returning the tensioner to said rest configuration after establishing the preload, the tensioner in said rest configuration being pressed toward one end of the extension portion; and comparing a difference between an initial length and a final length of the extension portion with a threshold.