| 摘要 |
PURPOSE:To improve quality and productivity by thread rolling with a usual way to a position near a shaft head, and then by thread rolling close to the shaft head by the part of a large lead angle formed at the end of rolling die. CONSTITUTION:In the first place, the usual thread rolling is performed by a screw thread 3 having a normal lead angle. Here, a blank 30 is fed to a chamfer 4 of die with a small clearance X between an under surface 33 of the head and an end face 8 of die, to roll to the part of a shaft 32 apart slightly from the head when it gets to the rear end part of the normal lead angle of the screw thread. Next, the die is further moved in the arrow direction and thread rolling is carried out to form the thread to the part close to the head 31 by the end screw thread 5 of the larger lead angle than normal one. In this way, the bolts threaded to close to the heads are efficiently manufactured. |
