| 摘要 |
PROBLEM TO BE SOLVED: To provide a self-drilling screw for ensuring discharge of cutting scraps without forming a thread in discharge grooves. SOLUTION: The self-drilling screw comprises an approximately conical drill part 11 formed on a non-screw part 10 of a leg 3, two-streak discharge grooves 20 formed in the drill part 11 and the non-screw part 10, and cutting edges 12, 14 ranging from the front end of the drill part 11 along the outer peripheral edges of the discharge grooves 20. A rising-gradient discharge inclined face 22 is formed on the rear side of the discharge grooves 20 ranging to the valley of a screw part 4, and a side wall 23 of the discharge inclined face 22 is upright from the discharge grooves 20. Thus, even when the drill part is formed and then a thread is rolled and shaped, the front end of the thread does not reach the discharge inclined face and so cutting scraps are smoothly discharged. Since the discharge inclined face is formed, the cutting scraps are moved rearward without being clogged while being gathered inside the discharge grooves. COPYRIGHT: (C)2009,JPO&INPIT
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