| 摘要 |
PURPOSE:To increase the height of a hole flange without cracking at the front end by forming thinly a prepd. hole part and shifting the material in the formed part to the circumference of the prepd. hole then blanking the prepd. hole and projecting a punch. CONSTITUTION:A plate 1 is drawn 2a to an approximately trapezoidal shape. The drawn shape is trapezoidal and the part of a prepd. hole 3a is made thin. The material in said part is shifted to the circumference of the hole 3a. This shin part is brought to the inside surface side of the trapezoidal shape. The hole 3a is formed by blanking and in succession a punch is projected to form a hole flange 4a. |
