Tapered friction stir welding tool

A friction stir welding tool comprising:

• a support body rotatable about a first axis, the support body having an end defining a shoulder;
• and
• a rotatable pin extending from the end of the support body downward from the shoulder,
• wherein the shoulder of the support body includes at least one section that is tapered, with the taper extending downward toward the pin.

A function stir welding tool comprising:

• a support body rotatable about an axis, the support body having an end defining a shoulder;
• a rotatable pin extending from the end of the support body downward from the shoulder;
• and
• a bottom support member connected to a distal end of the pin such that the pin is disposed between the support body and the bottom support member, wherein the bottom support member is rotatable about the axis and includes a bottom shoulder facing the shoulder of the support body, and wherein at least one of the bottom shoulder of the bottom support member and the shoulder of the support body includes at least one portion that is tapered,
• wherein if the bottom shoulder of the bottom support member is tapered, the taper extends from an outer edge of the bottom support member upward toward the pin, and
• wherein if the shoulder of the support body is tapered, the taper extends from an outer edge of the support body downward toward the pin.