Patent ID: 7188554

Claim:
A threaded fastener drive system, comprising: a screw fastener having a shank with a leading end, a head on the other end with a helical thread extending from said head to said leading end, a quadrilobe fitting on said head, said quadrilobe fitting forming a quadrilobe recess composed of four equally spaced columnar lobes, with the axis of each of said columnar lobes parallel with each other, each of said four columnar lobes connected to each other by a continuous sidewall forming a unitary curvilinear recess, a seat formed in said quadrilobe fitting, said seat having a substantially flat bottom of lesser diameter than said quadrilobe recess and a first continuous spherical transition wall between said bottom and said recess; and a drive tool having an elongated shaft having a first end and a second end, a quadrilobe drive tip connected to said first end of said shaft, said quadrilobe drive tip forming a quadrilobe protrusion, said protrusion composed of four equally spaced columnar lobes with the axis of each of said columnar lobes parallel with the longitudinal axis of said shaft, each of said four columnar lobes connected to each other by fillets forming an integral protrusion, said fillets being curvilinear whereby said quadrilobe protrusion closely engages said quadrilobe recess, and a first continuous spherical transition wall between said bottom and said recess; wherein said quadrilobe tip and said quadrilobe fitting each being of a size and shape to closely interlock whereby said shaft and said shank are coaxial during rotation of said helical thread.