Patent ID: 7401723

Claim:
A friction stir welding tool comprising: an integral shank-pin unit having an axial bore therethrough, a pin portion for plunging into at least one workpiece to perform a friction stir welding operation on the at least one workpiece, a shank portion for engagement with a chuck or collet of a friction stir welding tool, wherein the pin portion includes a tip, a base, and a tension member engagement feature in proximity of the tip, wherein the base being juxtaposition the shank portion; a shoulder removably connected to the integral shank-pin unit for preventing plasticized material from flowing out of the workpiece(s); and a tension member having a distal end with an engagement feature complimentary to the tension member engagement feature of the pin portion and a proximal end with an engagement feature, wherein the proximal end extends out of the axial bore of the integral shank-pin unit when the tension member is disposed within the axial bore of the integral shank-pin unit and the distal end engagement feature of the tension member is engaged with the tension member engagement feature of the pin portion; and an adjustable tension member engagement device to adjustably engage the proximal end of the tension member to simultaneously impose a predetermined inward axial force upon the tension member engagement feature of the pin portion and the shank portion of the integral shank-pin unit, thereby placing the pin portion in substantial compression between the tip and the base, whereby cyclic tensile stresses during friction stir welding are reduced.