| 摘要 |
PURPOSE:To facilitate the work for a female screw having a large diameter and permit the mass production of loosening-suppressing nuts by reducing the cutting torque by varying the root angle of the intermediate screw part or the front screw part and the intermediate screw part of a tap. CONSTITUTION:The ridge angle theta1 of the front screw part 3 of a tap 1 is set larger than the root angle theta of a female screw 6. The inclination of the flank surface is formed into two surfaces by making the ridge angle theta2 of an intermediate screw part 4 smaller than the root angle theta of the female screw 6, and the dimension and the sectional shape of a rear screw part 5 is made equal to those of the female screw 6. When the female screw is worked into a nut blank 10 by the tap 1, the revolution of the tap 1 is stopped by a stopper 9. When a prepared nut 11 is screw-fitted onto a bolt, the flank surface interferes, and a frictional force acts to develop the superior loosening-suppressing function. In case of the screw having the deformed intermediate screw part 4, the cutting torque is small, and effective for the work of a female screw having a large diameter. |
