| 摘要 |
The main body ( 2 ) of a self-drilling screw has a driven head ( 9 ) having at its top central region a weld lug ( 10 ) of a prescribed size. The screw also has a discrete drive head ( 3 ) having in its top a hole ( 11 ) for engagement with a driving tool. A thinned stud ( 12 ) continuing from the drive head ( 3 ) is resistance welded to the top center of driven head ( 9 ), using the weld lug ( 10 ) to form between these heads a torque-limiting junction ( 13 ) ready to break at a prescribed torque. As the main body ( 2 ) of the screw for use with thin steel sheets is tightened, the drive head ( 3 ) will be removed due to breakage of the junction ( 13 ). Any excessive tightening torque imparted to the screw will not break a female-threaded hole formed in the steel sheet, but firmly retaining the screw on it. |
