High security fastener

A security fastener for installation on a wheel having a recess hole extending from a recess entrance of a first diameter, comprising:

• a threaded end portion concentric with a longitudinal axis of said fastener;
• said threaded end portion configured and arranged to mate with a corresponding inner threaded element of said recess hole of said wheel when said fastener is installed in said recess hole;
• an intermediate skirt portion concentric with said longitudinal axis of said fastener and configured and arranged such that a side wall region of said skirt portion will extend within said recess hole when said fastener is installed in said recess hole;
• said side wall region of said intermediate skirt portion having a diameter within about 6 millimeters of said first diameter of said recess entrance;
• a drive portion having a tapered outer surface and a plurality of circumferentially spaced longitudinally extending key-receiving grooves in said tapered outer surface arranged in a lock pattern to which a driving torque may be applied;
• said drive portion configured and arranged such that said lock pattern will be exposed outside, at or inside said entrance to said recess hole when said fastener is installed in said recess hole;
• said tapered outer surface of said drive portion having a Rockwell scale hardness of about HRc 60 or less;
• said tapered outer surface sloping downward and outward away from said longitudinal axis of said fastener from a top surface substantially perpendicular to said longitudinal axis of said fastener to said skirt portion at a taper angle from said longitudinal axis of at least 11 degrees;
• and
• wherein said taper angle and said hardness of said tapered outer surface of said drive portion are governed by the function:
• taper angle≧11.25+((60−taper hardness)*0.75),
• where “taper hardness” is said Rockwell scale hardness of said drive portion.

A security fastener for installation on a wheel having a recess hole extending from a recess entrance of a first diameter, comprising:

• a threaded portion concentric with a longitudinal axis of said fastener;
• said threaded portion configured and arranged to mate with a corresponding threaded element of said recess hole of said wheel when said fastener is installed in said recess hole;
• a drive portion having a tapered inner surface and a plurality of circumferentially spaced longitudinally extending key-receiving grooves in said tapered inner surface arranged in a lock pattern to which a driving torque may be applied;
• said drive portion configured and arranged such that said lock pattern will be exposed outside, at or inside said entrance to said recess hole when said fastener is installed in said recess hole;
• said tapered inner surface sloping downward and inward toward said longitudinal axis of said fastener at a taper angle from said longitudinal axis of at least 11 degrees.