A method for manufacturing a long length of coiled metal tubing or the like using friction stir welding. Successive lengths of metal strip are friction stir welded using a three-pass welding technique to eliminate any edge defects in the resulting strip. The method includes one or more three-pass friction stir welding routines, each of which includes a first pass performed using a tool having a first rotational direction and a spiral bit pattern corresponding to the first rotational direction; a second pass using a tool having a second rotational direction and a spiral bit pattern corresponding to the second rotational direction; and a third pass using a tool having said second rotational direction and a spiral bit pattern corresponding to the second rotational direction.