Patent ID: 8001874
Filing Date: 2011-08-23
Classification: B21K,B25B,F16B

Abstract:
1. A combination of a screw with stabilized strength and a screwdriver bit, wherein: in said screw with stabilized strength; a screw head of said screw is provided with a bit engaging groove that is formed in a Y shape divided into three equal parts in a circumferential direction at a specified radial distance from a central portion of said screw head, said screw head being formed in a shape of a pan, groove widths of respective branching grooves that extend in a radial direction from a central portion of said bit engaging groove are formed so that said widths gradually expand, thus producing substantially equal intervals with a width dimension of boundary portions which are between respective adjacent branching grooves being of substantially a same dimension as a width of the branching grooves, respective outer circumferential end wall surfaces of said bit engaging groove are formed in a substantially perpendicular attitude to a specified depth from an opening edge part, and step parts sloped downward toward a central portion of a screw neck from perpendicular lower edge portions are respectively provided from said specified depth to a bottom of an intersecting central portion of the bit engaging groove, the opening edge part of the respective outer circumferential end wall surfaces of the bit engaging groove is formed as an inclined surface that inclines upward at an angle of 15° to 35° from an inner diameter side toward outwardly radial direction, the bottom of the intersecting central portion of the bit engaging groove is formed as a bottom surface which is a circular conical recessed part provided thereon, and boundary portions between the respective adjacent branching grooves of the bit engaging groove are formed so that the boundary portions are formed by planar side wall surfaces that intersect at obtuse angles showing left-right symmetry with respect to respective branching grooves in the central portion of the bit engaging groove, and a surface of said screw head that forms said boundary portions is formed as an inclined surface portion that is inclined at an angle of 20° to 50° downward toward the central portion of said bit engaging groove; and said screwdriver bit comprises a tip end blade part, vane parts, inclined surface and step parts, and protruding parts, wherein said vane parts are respectively formed on said tip end blade part and have end edge parts that have a right-angled shape to obtuse angular shape and engage with respective branching grooves of said bit engaging groove formed substantially vertically from an opening edge section thereof and in a Y shape divided into three-equal parts in the circumferential direction in said screw head of said screw with stabilized strength, said inclined surface and step parts are respectively formed on tip ends of said respective vane parts so as to match the step parts of said bit engaging groove, and said protruding parts are formed to intersect and connect in a circular conical shape in a central axial part of the screwdriver bit, said protruding parts corresponding to the bottom surface of the circular conical recessed part.