PURPOSE: To easily practice a piercing work for a relatively short sized material, by pushing a piercing plug into a round bar shaped blank along its central axis in order to apply a piercing work, while rotating and pressing the round bar shaped blank with a couple of press rolls rotating in the same direction.
CONSTITUTION: A short sized, round bar shaped blank S is put between a piercing plug 9 and a blank holding jig 71, and is rigidly clamped by upper and lower rolls 1, 2. The upper and lower rolls 1, 2 are rotated in the same direction, and their roll gap is narrowed. Hereby, one or more turns of rolling compression are given to the blank S. At the same time, a plug 9 is pushed into the blank S along its central axis, that is, the piercing work is applied to the blank S. Since the pierced part Sa of the blank S is restrained by guides 8, the flattening deformation of the pierced part Sa is restrained. The press rolls 1, 2 are then released from the load, their roll gap is widened, and the blank S is finished between the guides 8. Moreover, by attaching suitable dies to the surface of upper and lower rolls 1, 2, a stepped uneven pattern is formed in the surface of the blank S.
ARITA MASAJI
IKE MASAHIDE
SATOU SHINTAROU
