Stick fit fastener recess system

A fastener system comprising:

• a. fastener having
• i. a shank having a central shank longitudinal axis;
• ii. a head at an end of the shank;
• iii. the head having a recess centered on the shank axis;
• iv. the recess having a plurality of wings radiating outwardly from the shank axis, the recess having a recess outer radius defined by a radial distance from the shank axis to the outer-most extent of the wings;
• v. each of the wings having an installation driving surface and a removal driving surface, the wing driving surfaces being constructed in substantially parallel alignment with the shank longitudinal axis;
• vi. the installation driving surface and removal driving surface of adjacent wings being separated by a respective transition contour, the transition contour forming the radially inward-most portions of the wings;
• vii. a wedge formed in the transition contour to present a tapered recess interface surface, the interface surface having a top, a bottom and a pair of opposed edges, the width of the interface surface tapering from wider at the top of the interface surface proximate a top of the recess to narrower at the bottom of the interface surface proximate a bottom of the recess;
• and
• viii. the interface surface positioned a root radial distance from the shank axis at the bottom of the interface surface, the root radial distance defining the recess inner radius, the interface surface positioned a top radial distance from the shank axis at the top of the interface surface, the top radial distance being larger than the bottom radial distance;
• b. a driver having a bit end, the driver having a central driver longitudinal axis, wherein the bit end is constructed having a central portion and a plurality of lobes radiating outwardly from the central portion, the bit end having a dimension AT bit diameter extending from ends of lobes on opposite sides of the driver bit, each of the lobes having an installation driving surface and a removal driving surface, installation driving surfaces and a removal driving surfaces of adjacent lobes separated by a transition contour, the transition contour forming the radially inwardly most portions of the lobes and presenting a driver interface surface, and wherein the surfaces of the lobes are constructed in parallel alignment with the driver longitudinal axis;
• c. wherein the recess receives the bit end, and the driving surfaces of the fastener head can receive the driving surfaces of the driver bit end in a mated engagement along a driver lobe engagement length, and the recess interface surfaces and driver interface surfaces are constructed to form a frictional engagement such that interference regions are formed between the recess interface surfaces and the driver interface surfaces when the fastener head and driver bit end are in mated engagement;
• and
• d. the ratio of the lobe engagement length to the bit diameter being from about 0.15 to about 0.21.