| 摘要 |
PURPOSE:To form a forward drawn or straight central hole to a cylindrical body in cold forging the hole part to said body by forming the projecting part at the top end of a molding formed by extrusion into the forward divergent shape having a central mandrel and drawing the outside diameter of the projecting part by a knocking out process. CONSTITUTION:A pin 20A for punching and extrusion is moved upward to form a projecting central hole body 42 at the same instant when a blank material M is inserted into a die 10 and an extruding punch 50 is forced therein. The projecting part 11 of the die 10 is forward divergent. When a ring ejector 30 is knocked out by retreating the pin 20A, a forward divergent part 42 is drawn straight and a fine hole 41a is made into the forward drawn hole. If the pin 20A is tapered, the hole 41a is made straight. The forward drawn fine hole and straight deep hole which are impossible to be worked by cold forging are easily forged by the above-mentioned method. |
