| 摘要 |
PURPOSE: To prevent a flash by expanding a parting line face outside a longitudinal direction center axis of an expanding sleeve so that the expanding sleeves having even number segments of four or more are turned to a state a profile part outside the parting line is closed in expanding. CONSTITUTION: The expanding sleeve having a punch 8 and an expanding sleeve 9 is provided with a punch hole 15, into which a free end part of the punch is fitted in tight contact, and segments 11, 12 movable in a radial direction having an outside profile corresponding to an inner face shape of a work separated by a parting line. The parting lines are formed by boundary faces of the neighboring segments. When the expanding sleeve 9 having even number segments 11, 12 of four or more is expanded, the parting line 18 face is expanded outside a longitudinal direction center axis of the expanding sleeves 9 so that a profile part outside the parting lines 18 is turned to a closed state. By this method, a flash is not generated, a process to remove the flash is not required. |
