METHOD AND DEVICE FOR PIERCING BY PLASTIC WORKING

PROBLEM TO BE SOLVED: To provide the method and device by which the secure and precise piercing working of a very small diameter is efficiently performed to small parts by plastic working. SOLUTION: A bar-shaped work piece W2 is inserted into the hole part of a first die. By facing the first die and a first punch each other and making them approach, on one end face of the barshaped work piece, a spherical surface recessed part E whose alignment was performed by a spherical surface projecting part of a first die pin, is formed. Next, after detaching the first die and the first punch, by facing the first die and a second punch each other and making them approach, after forming a shallow hole (h) by a first piercing tool on another end face of the bar-shaped work piece, while holding the bar-shaped work piece by the second punch, by facing the second punch and a second die 51 each other and making them approach, the bar- shaped work piece is inserted into the second die. After detaching the second die and the second punch, by facing a third punch 91 and the second die each other and making them approach, while one end face of the bar-shaped stock piece is borne, making the spherical surface recessed part after alignment a space, a deep hole is formed in a shallow hole on another end face by a second piercing tool 96a.