Patent ID: 7748593

Claim:
A friction stir welding apparatus comprising: a rotary tool whose extremity constitutes a probe; a retaining arm which supports the rotary tool; and a roller provided at a position of the retaining arm opposite the rotary tool, said roller being disposed substantially directly opposite to said rotary tool; wherein said roller is a caster roller which is operable relative to a couple of axes which are perpendicular to each other, one of said axes being parallel with a rotation axis of the rotary tool; and wherein another of said axes of the caster roller is arranged at a position offset by a preset distance from the rotation axis of the rotary tool such that during three-dimensional friction stir welding operation of workpieces, a supporting point of the caster roller which comes in contact with the workpieces is maintained at a constant distance from the rotation axis and on a circular path having a predetermined radius about the rotation axis of the rotation tool.