| 摘要 |
PURPOSE:To enhance the insertion ability during drilling, the fastening ability during seating and the finishing treatment after completion of fastening to a member to be fastened, by improving the shape of the head part of a drilling screw. CONSTITUTION:A head part 6 is composed of a large diameter part 13 having an upper surface 9 which is a spherical recess surface formed therein with engaging grooves in which a driver tool is engaged, and an outer peripheral surface formed therein with an inverted truncated conical shape first seat surface 12 which is a concave recess surface, and a small diameter part 15 which is concentrically and integrally incorporated with the larger diameter part 13 therebelow and having an outer peripheral surface forming therein a truncated conical shape second seat surface 14. The joint part between two-stage concave recess seat surfaces is formed thereon which an annular projection 16. Further, the upper surface 9 of the head part 6 formed therein with the spherical recess surface is formed therein with a chamfered part 17 which is obtained by conically cutting the opening edge part of the engaging grooves 10 constituting a cruciform groove. Further, a plurality of counterboring ridges 19 are formed on the second seat surface 14, extending along the concave recess surface.
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