| 摘要 |
A tapping screw having a shank having a head and a tapered tip portion. The shank is formed on its peripheral surface with threads. First and second drill edges are formed on the tapered portion and on the intermediate portion between the head and an tapered portion, respectively, so as to be independent of the threads. The first drill edge has a maximum diameter smaller than that of the threads in the rear thereof and the second one has a maximum diameter equal to or larger than that of the threads on the main portion of the shank. |
