Apparatus for friction stir welding

An apparatus for friction stir welding, said apparatus comprising:

• a pin configured to be driven in a rotating manner about an axis of rotation and including a drive end and a free end,
• wherein between the drive end and the free end a cylindrical engaging portion is provided, with the engaging portion extending axially in the direction of the axis of rotation, and including a circumferential surface configured for engagement with one or more workpieces;
• a first shoulder element arranged on a side of the engaging portion that is adjacent the drive end and is arranged concentrically around the pin with respect to the axis of rotation, said first shoulder element including a first bearing surface that faces the engaging portion and extends perpendicularly to the axis of rotation;
• a second shoulder element arranged on a side of the engaging portion that is adjacent the free end and is arranged concentrically around the pin with respect to the axis of rotation,
• said second shoulder element including a second bearing surface that faces the engaging portion and extends perpendicularly to the axis of rotation,
• wherein the second bearing surface extends to the engaging portion,
• wherein the first shoulder element and the second shoulder element are configured to bear against opposite, respective first and second surfaces of the one or more workpieces;
• and
• a bearing element rotatably interconnecting the pin and the second shoulder element so that the pin is rotatable relative to the second shoulder element about the axis of rotation, thereby permitting the second shoulder element to remain stationary with respect to the surface of the at least one workpiece while the pin rotates,
• wherein the second shoulder element is formed as a sleeve with a bottom surface extending radially to the axis of rotation and a cylindrical side wall extending parallel to the axis of rotation, the second bearing surface being formed in the bottom surface,
• wherein the free end of the pin is surrounded by a cylindrical carrier, which is adjustable in the axial direction of the pin, and wherein the sleeve is mounted on the carrier so as to permit relative rotation therebetween,
• wherein the bearing element includes a ball bearing provided between the side wall and the free end of the pin,
• wherein the free end of the pin is provided with a thread, and the carrier is configured to be screwed onto the free end, so that the pin is connected to the second shoulder element in an axially adjustable manner,
• wherein the carrier has a threaded bore extending perpendicularly to the axis of rotation for receiving a fixing screw, and a bore aligned coaxially in relation to the threaded bore is formed in the side wall of the sleeve.