| 摘要 |
PURPOSE:To prevent crack, when pressure inserting a valve seat into a valve seat step section having tapered open edge, by bending said open edge simultaneously through a punch which can plastic work a curved face. CONSTITUTION:When pressure inserting an annular member 3 to be used as a valve seat into a valve seat insertion step section 2 of cylinder head 1, a zig 5 for pressure inserting said member 3 is formed by means of a punch which can plastic work the open edge of said step section into curved face simultaneously with pressure insertion of said member 3. Consequently the open edge of valve seat can be formed into curved face which is not subjected to crack without requiring additional process, thereby it can be worked to highly hard composition which is not deformed thermally. |
