Patent ID: 7793816

Claim:
A friction stir welding apparatus comprising: a first member having at least one bearing surface for rotatably receiving a friction stir welding tool; a second member having at least one bearing surface for rotatably receiving the friction stir welding tool; the friction stir welding tool having a first bearing surface rotatably coupled to the at least one bearing surface in the first member, before the tool is inserted into at least one of two work pieces, and a second bearing surface rotatably coupled to the at least one bearing surface in the second member, before the tool is inserted into the at least one of two work pieces; and an engagement member coupled to at least one of the first member and the second member, wherein the engagement member is adapted to apply an engaging force in a direction perpendicular to the longitudinal axis of the friction stir welding tool to engage the at least one of two work pieces to provide torque compensation for the friction stir welding apparatus while the friction stir welding tool is rotating.