| 摘要 |
<p>A tapping screw capable of being easily driven into a thick wall material reliably prevented from untightening in order to use it as a stud bolt and the like. Main threads (2, 2') are dividedly formed on the distal end and the proximal end of a tapping screw, and auxiliary threads (3) opposite in direction to the main threads are provided therebetween. The outer diameter of the auxiliary threads (3) is substantially equal to the diameter of a prepared hole, and the gradient of the slope of the auxiliary threads is formed such that the gradient is gentle at the slope (3a) on the tightened side and sharp on the slope (3b) on the untightened side. The main threads (2) on the distal end are driven in as a tapping screw, and subsequently, the oppositely directed auxiliary threads (3) are driven in like a wedge, and finally, the main threads (2') on the proximal side are driven in. Since the main threads and the auxiliary threads are formed separately from each other, the drive-in torque becomes not large, and, even if a torque in the untightening direction acts on after tightening, the auxiliary threads (3) work against this action to thereby prevent untightening.</p> |
