| 摘要 |
The screw has a stem (1) with a thread (3), a drive head, a point (2) and a rounded transition between thread flank pitch (4, 5) and the stem point. The ratio between the outer dia. and the core dia. of the screw is greater than conventional. Typically two diametrically opposed scraping grooves (6) may have the form of a longitudinal notch with two limit surfaces at a right angle. The scraping groove passes through the thread as far as the screw core, ending in front of the rear end of the screw point. |
