| 摘要 |
<p>It comprises a drill-point (3) with a diameter of between 60% and 70% of the nominal thread (2) diameter; the screw has a transition zone (4) of at least three turns (41,42,43,44) of thread between the drill-point (3) and the nominal thread (2) diameter. It permits firm fixing in thin sheets, and at the same time it is quick and easy to fit. <IMAGE></p> |
