Arcuate tip driver

A driving tool for use in combination and relative high torque engagement with a fastener having a head at one end of a threaded shank, said head having a driving face in which is recessed a driving slot of generally bow tie configuration defined by at least slightly undercut side walls and an arcuately concave bottom wall having a radius of curvature centered on the longitudinal axis of the shank, the slot having a length which is the distance between the intersections of the bottom wall with the driving face as measured along the driving face, said driving tool comprising:

• a tool shaft having a longitudinal axis, a driving blade at one end of said shaft defined by front and rear surfaces and a pair of side surfaces and an arcuately convex distal end surface intersecting said front and rear surfaces and said side surfaces, each of said front and rear surfaces being arcuately concave about an axis of curvature which is disposed substantially parallel to said longitudinal axis of said shaft, each of said front and rear surfaces being arcuately concave about an axis of curvature which is substantially orthogonal to the longitudinal axis of the shaft, said blade having a width which is the distance between said side surfaces at their intersections with said end surface, said end surface having a radius of curvature centered on said longitudinal axis of said shaft, said width of said blade being substantially less than the length of the slot, said radius of curvature of said blade end surface being greater than the radius of curvature of the bottom wall of the slot.