FORMING METHOD OF ANNULAR GROOVE ON OUTER PERIPHERY OF METAL TUBE AND DIE FOR FORMING SAID GROOVE

摘要

PURPOSE:To form annular groove without torsion and deformation by making the center of a die eccentric to the center of the metal tube progressing at a fixed speed and by rotating with press the blade tip of a die so as to bite in the outer periphery of the metal tube. CONSTITUTION:The distance P2P2' between the blade tip point P2 of an arcuate blade 4a and the blade tip point P2' of a circular blade 3 enables to feed necessarily and sufficiently between P2P2' the metal tube stock necessary for the formation of the groove for one pitch part compared to the pitch PT of the groove 7 to be formed. The blade tip point P3' of the circular blade 3 then forms the groove in the direction (a) and simultaneously due to the inclined face CD of the groove being pressed to the counter direction (b) by the side face in the direction (b) of the circular blade 3 the groove crest part of around the point (c) is forced up in the direction (a). The groove crest part thus formed is formed as a complete groove crest at the groove forming time of the following cycle and the height of said groove crest is made same as the height of the groove crest part formed by the circular blade 3 of until the groove formation by the arcuate blade 4a is started.