Abstract: A method and apparatus is disclosed for forming a friction stir weld joint using a friction stir tool. A first metallic work material and a second metallic work material are provided and are substantially abutted to define a joint interface having a weld surface. A quantity of metallic donor material is provided and deposited into a depression formed in the weld surface along the joint interface. A friction stir welding tool having a shoulder and a pin depending from the shoulder is provided and applied against the donor material within the depression using a plunge force. The friction stir welding tool is rotated such that the pin contacts the donor material and heats the donor material to plasticize at least a portion of the donor material forming a friction stir weld joint. The friction stir welding tool is then urged along the joint interface.