WORKING METHOD FOR BRANCH PIPE

PURPOSE:To prevent wall thickness reduction, to increase stiffness, to eliminate beveling, and to improve productivity by restraining the open end of a branch pipe at a specified height and moving a branch material laterally for branch pipe forming by pushing a pipe material or plate material in the radial direction or the rectangular direction to the thickness direction. CONSTITUTION:A branch pipe 2 is formed by punching a pipe material 1 by a mandrel 5. In that time, the open end 9 of the branch pipe 2 is restrained at a specified height by a beam 10 fixed and supported by a leg 12 and is moved laterally. Prevention of the wall thickness reduction of the branch pipe 2 increases its stiffness. Also, a uniform bevel end height eliminates beveling, increases working efficiency, and improves productivity. The beam 10 is pressed by a cylinder or is controlled and pressed by a spring so as to control a uniform wall thickness and a uniform end height of the branch pipe.