Apparatus for manufacturing internal grooved tube

An apparatus for manufacturing an internal grooved tube comprising:

• a rotary die which rotates in a predetermined direction;
• a plug inserted in a metal blank tube which is put through said rotary die and drawn therefrom and performs a diameter-reducing work on said metal blank tube together with said rotary die;
• a grooved plug rotatably coupled onto an axial line of said plug in a direction of a distal end thereof through a plug rod and having multiple axial-directional or spiral grooves formed in an outer surface;
• a working head which is provided in such a way that said metal blank tube passes inside at a position of said grooved plug, has a conical internal surface formed inside that becomes wider in a drawing direction of said metal blank tube, and rotates independently of said rotary die;
• a plurality of balls which are retained inside said working head in such a way as to rotate in contact with an outer surface of said metal blank tube and said conical internal surface to be pressed against said outer surface of said grooved plug through said metal blank tube, and revolve on the same circular orbit about said metal blank tube as said working head rotates;
• a first lubricating-oil feeding unit for feeding a lubricating oil to a work portion of said rotary die from an upstream side in said drawing direction of said metal blank tube;
• and
• a second lubricating-oil feeding unit for feeding a lubricating oil to a work portion of said working head from an upstream side in said drawing direction of said metal blank tube.