EXTRUDED-FORMING APPARATUS FOR DRILL INTERMEDIATE PRODUCT HAVING TWIST HOLE

摘要

PURPOSE:To form a drill intermediate product having twist hole at high efficiency and high accuracy by making twist roundish regular polygon cross sectional shape of the hole in straight part of the die and arranging pin for forming the twist hole, in which the twist angle is gradually increased. CONSTITUTION:The die for extruded forming apparatus is composed of approach part 4 and straight part 5. The hole 6 in the straight part 5 is made to the regular polygon cross sectional shape having roundish at each other part and turning at more than 90 deg. to reach to the end part with leading angle. At the inlet part of this die 1, the flange 2 composing of ring-like part 7 and bridge-like pin supporting part 8 is fitted. A large diameter part 10 reinforced with the pin 3 is fixed to the pin supporting part 8. The tip part 11 thereof is spirally twisted to the same direction as twist direction of the hole 6 while holding at the fixed distance from the axial center of the die 1 to constitute the pin for forming the twist hole. Further, the leading angle of the above hole 6 and the twist angle of the pin 3 are gradually increased toward outlet of the die 1. Then, the twist angle of the pin 3 is made to smaller thin the leading angle of the hole 6 under consideration of the twist by pushing pressure.