screw

Abstract

The article relating to this design is a screw having a deformed hexagonal bit fitting hole formed on the top surface of the countersunk screw head, and is provided with bit fitting grooves that extend in six directions in an arc shape at equal angles radially from the center of the bit fitting hole, and (1) the tip portions of each of the grooves extending in the six directions are extended in a parallel manner to form an inclined surface at a required angle that is directed downward from the top opening edge of the bit fitting hole toward the center, and (2) each of the six grooves that are adjacent to each other in the bit fitting hole toward the center side The screw design is formed such that the grooves are adjacent to each other in a curved shape, (3) for each groove forming the bit fitting hole, a straight groove is formed that is of equal width and linearly crosses any pair of opposing grooves surrounding these grooves and extends radially outward to fit a flathead screwdriver bit, (4) several cylindrical recesses that form the inscribed circles of the grooves are formed on the central side of each groove that extends in the six directions of the bit fitting groove, and (5) the bottom of these cylindrical recesses is formed with a substantially frustoconical base surface that is directed downward from its center.

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