| 摘要 |
PURPOSE:To reduce the dispersion of the rectangularity between the thread part and seat surface under a bolt head by making the simultaneous form-rolling of a recess part under the bolt head and the thread part with a rolling die in which a die for working the part under the head is integrated with a die for working a thread. CONSTITUTION:A connecting rod bolt 11 made of cold forged stock is set in a rolling die 21 or located between a fixed die 22 and a mobile die 23. Then, the mobile die 23 is moved by a prescribed amount toward the side of the fixed die 22 to compress the cold forged stock by the fixed die 22 and the mobile die 23. Under this state, the mobile die 23 is moved toward the direction of an arrow A and advanced toward the direction of the arrow A while rolling the connecting rod bolt 11. For this reason, the recess part 16 under the head and the thread part 19 are form-rolled simultaneously in the connecting rod bolt 11. At this time, the cold forged stock is stretched in the direction of an arrow B together with form-rolling of the thread part 19, the seat surface 15 of the head part 12 sticks to the seat surface and the working surface 24c 26c of the fixed die 22 and the mobile die 23 and the rectangularity of the seat surface 15 to the axial center C of the bolt is formed with extremely high accuracy. |
