| 摘要 |
PROBLEM TO BE SOLVED: To provide a tapping screw for forming a thread ridge capable of penetrating at least two stacked metal plates with a total thickness of at least 2 mm without generating shavings. SOLUTION: The tapping screw 10 is provided with a pointed end 13 and a head 14 at both side ends of a shaft provided with a thread ridge 15 at least in part, and has an acute truncated cone shaped part 21 and a cylindrical part 25 in this order from the pointed end 13 toward the head 14. A first rugby ball shaped part 22 having a first radius of curvature R1 is placed adjoining the head 14 side of the acute truncated cone shaped part 21, and a second rugby ball shaped part 24 having a second radius of curvature R2 is provided between the first rugby ball shaped part 22 and the cylindrical part 25. The first radius of curvature R1 and the second radius of curvature R2 are made different in size. It is preferable to provide a truncated cone shaped transition part 23 between the first rugby ball shaped part 22 and the second rugby ball shaped part 24. COPYRIGHT: (C)2008,JPO&INPIT |
