Abstract: A workpiece having a first constant diameter portion, a tapered reduced-diameter portion, a concave portion, a tapered increased-diameter portion, and a second constant diameter portion is formed by machining the tapered reduced-diameter portion, and then machining the tapered increased-diameter portion and the concave portion.

Abstract: A workpiece having a first constant diameter portion, a tapered reduced-diameter portion, a concave portion, a tapered increased-diameter portion, and a second constant diameter portion is formed by machining the tapered reduced-diameter portion, and then machining the tapered increased-diameter portion and the concave portion.

Abstract: A method of manufacturing a cylindrical body, comprising the step of forming the cylindrical body by bending a plate-like work having first projected finger to fourth projected finger at four corned parts and allowing the end faces thereof to abut on each other, wherein the main surface of the cylindrical body on the side where sags are present is formed in an outer peripheral wall surface and the rear surface thereof on the side where the burrs are present is formed in an inner peripheral wall surface, and a first projected part is formed of the first projected finger and the third projected finger and a second projected part is formed of the second projected finger and the fourth projected finger. After the cylindrical body is held by friction stir welding devices, the probe of a friction stir welding tool is buried from the direction of either of the first projected part and the second projected part, and scanned in the direction of the other of the second projected part and the first projected part.

Abstract: A friction stir welding apparatus (120) brings end faces (1, 2) of a plate material (W1), having fingers (7a through 7d) at corners thereof, into abutment against each other to form a hollow cylindrical body (W2), and friction-stir-welds the end faces (1, 2) to each other. The apparatus includes a base (122), a first support device and second support device which are mounted on the base (122), a support core (32) spaced from the base (122) by the first support device and the second support device, for insertion into the hollow cylindrical body (W2) and for supporting the hollow cylindrical body (W2), and a first gripping member (238) and a second gripping member (268) disposed on the support core (32) for gripping respective protrusions (8, 9), which are formed when the fingers (7a through 7d) are held in abutment against opposite ends of abutting regions of the hollow cylindrical body (W2), and which extend along a joining direction.

Abstract: A friction stir welding apparatus (120) brings end faces (1, 2) of a plate material (W1), having fingers (7a through 7d) at corners thereof, into abutment against each other to form a hollow cylindrical body (W2), and friction-stir-welds the end faces (1, 2) to each other. The apparatus includes a base (122), a first support device and second support device which are mounted on the base (122), a support core (32) spaced from the base (122) by the first support device and the second support device, for insertion into the hollow cylindrical body (W2) and for supporting the hollow cylindrical body (W2), and a first gripping member (238) and a second gripping member (268) disposed on the support core (32) for gripping respective protrusions (8, 9), which are formed when the fingers (7a through 7d) are held in abutment against opposite ends of abutting regions of the hollow cylindrical body (W2), and which extend along a joining direction.

Abstract: A method of manufacturing a cylindrical body, comprising the step of forming the cylindrical body by bending a plate-like work having first projected finger to fourth projected finger at four corned parts and allowing the end faces thereof to abut on each other, wherein the main surface of the cylindrical body on the side where sags are present is formed in an outer peripheral wall surface and the rear surface thereof on the side where the burrs are present is formed in an inner peripheral wall surface, and a first projected part is formed of the first projected finger and the third projected finger and a second projected part is formed of the second projected finger and the fourth projected finger. After the cylindrical body is held by friction stir welding devices, the probe of a friction stir welding tool is buried from the direction of either of the first projected part and the second projected part, and scanned in the direction of the other of the second projected part and the first projected part.