To provide a working method by which excellent accuracy in dimension, shape and surface roughness are secured even when using inexpensive welded tube and utilizing efficient parallel swaging and which contributes to the reduction of the cost and the improvement in productivity, and to provide a suitable working device to utilize this working method.
After inserting a mandrel 23 into a tube stock 20 consisting of an electrically welded tube, the parallel swaging is performed by moving a cylindrical die 24 and the end part of a tube stock 20 is closely adhered to the parallel forming part 27 of the mandrel 23. After completing the parallel swaging, the die 24 is pulled out of the tube stock 20, a pushing die 33 is made to approach the tube stock 20 from the outside direction of a radius, and the weld bead part of the tube stock 20 is crushed in cooperation with the mandrel 23, while leaving the mandrel 23 in the inside of the tube stock 20.
KAMIYAMA MASARU
Toshio Nakamura
Miyazaki Yoshio
Kaoru Onozuka