Friction stir welding device

A friction stir welding device comprising:

• a pair of workpiece surface plates between which a gap extending along a welding line between workpieces is formed and which are provided on a frame;
• a welding device body;
• a main spindle provided in the welding device body;
• a friction stir welding tool protruding upward from the gap and attached to an upper end of the main spindle;
• a drive device that rotates the main spindle provided in the welding device body;
• a linear guide mechanism that supports the welding device body so as to be movable in a direction along the gap;
• and
• a moving device that moves the welding device body in the direction along the gap including:
• a first set comprising a first rack and a first rack meshing gear;
• and a second set comprising a second rack and a second rack meshing gear, wherein the first rack and the second rack are located below the workpiece surface plates on the frame so as to extend in a direction parallel to the gap, and the first rack meshing gear and the second rack meshing gear individually mesh respectively with the first rack and the second rack, and wherein the first rack meshing year and the second rack meshing gear are each rotatably mounted in the welding device body,
• wherein the first set comprising the first rack and the first rack meshing gear and the second set comprising the second rack and the second rack meshing gear are disposed spaced apart from each other on opposite sides of a position immediately below a tool movement path along which the friction stir welding tool moves accompanying movement of the welding device body, and
• teeth of the first rack meshing gear deviate from teeth of the second rack meshing gear by a half pitch.