| 摘要 |
PURPOSE:To prevent breaking-off of a formed piece, by forming a relief face at an intersection of the inner face of a formed piece and a contact face so as to remove the corner. CONSTITUTION:When forging, pressure is applied outward in the forming hole, and this pressure becomes maximum at the center of each side of a hexagon. Consequently, the inside face 20a of each formed piece 20 is deformed to bent outward. Since a relief face 20d is formed, an intersection of inside face 20a and the relief face 20d does not collide with adjoining formed pieces 20. Accordingly, the formed piece 20 is hard to be broken. It is enough to form the relief face only in one of the adjoining formed pieces 20. |
