Drilling and tapping screw

Claim 1

A drilling and tapping screw structure comprising: a slender shank; cutting screw thread means extending helically on an outer periphery of said shank; tool receiving means formed at a rear end of said shank; a drill portion integral with a front end of said shank, said drill portion having a cross-section comprising a central portion and two integral protrusions wherein said protrusions extend from opposite sides on opposite ends of said central portion, said cross-section defined by short side portions and long side portions, wherein each of said long side portions is comprised of a planar portion and a gently curved guide portion which forms said protrusions, said drill portion extending from said shank in a substantially truncated shape form with said long side portions having a base portion, said base portion having a diameter slightly larger than a diameter of said shank and slightly smaller than a diameter of said shank including said cutting screw thread means, said base portion diameter progressively increasing in a direction away from said rear end of said shank to a maximum diameter slightly smaller than said diameter of said shank including cutting screw thread means; a tip positioned on an axis of said shank on said drill portion, said tip being comprised of a pair of tapered cutting faces, wherin said faces form a sharp edge and are symmetrically positioned with respect to an outermost point of said tip, with each of said faces having a width which progressively increases in a direction away from said outermost point; and a pair of ribs respectively formed centrally on said long side portions, said ribs extending longitudinally from said front end of said shank, said ribs narrowing in a direction away from said shank and having a peripheral surface and length about one-half the axial length of said drill portion.