| 摘要 |
PURPOSE:To reduce processing labor and to facilitate mass production by inserting a core in a small diameter part and setting the connection part of the small diameter part and a large diameter part to a positioning part and pressing a punching body from the outside of the small diameter part to bore an air hole. CONSTITUTION:A metal shaft body 10 has a large diameter part 11 and a small diameter part 12 and the large diameter part 11 is inserted in the hole 21 of a holder 20 to be held thereto. When downward force is applied to a jacket body 80, a guide member 40 does not move because it is in contact with the metal shaft body 10 but a cam 70 and the jacket body 80 is displaced downwardly against the elastic force of an elastic member 90. A punching body 50 itself is limited from downward displacement because it is inserted in the hole 43 of the guide member 40 but, since a rear end part 52 comes into contact with the taper surface of the cam 70 in a slidable manner, the punching body 50 is displaced toward the internally present metal shaft body 10. The punching body pierces the side wall of the small diameter part of the metal shaft body 10 by this displacement when the downward displacement quantity of the jacket body 80 is increased. |
