A screw nail includes a nail shaft portion extending along one direction, and a head portion whose diameter is enlarged along other direction orthogonal to an extension direction. A sharp tip end portion is formed on one end side of the nail shaft portion, and the head portion is formed at an end portion on the other end side. The nail shaft portion is formed with a screw thread, and the head portion is formed with an engaging portion capable of engaging with a rotary tool. A convex portion protruding along an axis direction of the nail shaft portion is formed on an end surface of the head portion. A concave portion that is concave with respect to the convex portion is formed between the convex portion and the engaging portion. A virtual plane specified by vertexes of the convex portion is a plane orthogonal to the axis direction.

A bolt includes a head portion on which a recess is formed. The recess has a bottom surface and a sidewall extending from a periphery of the bottom surface. The sidewall has a lower end defined by the bottom surface and includes an increased diameter portion and a reduced diameter portion. The increased diameter portion has an inner diameter larger than an inner diameter of the lower end of the side wall. The reduced diameter portion has an inner diameter smaller than the inner diameter of the increased diameter portion. The reduced diameter portion is located opposite to the bottom surface across the increased diameter portion.

In one embodiment, a fastener includes a flexible head and a shank coupled to the flexible head. The flexible head includes a center head portion and a plurality of wing portions coupled to the center head portion. Each of the plurality of wing portions includes a contact area configured to contact a first surface of a part to be fastened. The shank includes a clip groove configured to hold a retainer clip against a second surface of the part to be fastened. The second first surface of the part to be fastened is opposite the first surface of the part to be fastened.

A socket having an offset drive keyway for transmitting torque to asymmetric fastener heads to facilitate their rotation by applying torque across the fastener end to minimize stress on the fastener end-fastener shaft joint.

This present invention relates to a dual head screw that features at least one male nut driver extending outwardly from a base head opposite the shaft of the screw. The dual head screw replaces standard female head screws, thus eliminating concern over stripping of the screw head or the same becoming compacted with debris. The dual head screw has a shaft with a threaded section, a base head and the male nut driver. The male nut driver is dimensioned in size to withstand the torsional forces associated with installing or extracting the dual head screw from an object, and may be driven or extracted with a standard hand tool or a power drill. In a further embodiment, the male nut driver may be comprised of a first driving portion and a second driving portion.

An anti-theft screw part includes an annularly extending recess for engaging an adapter, which as viewed from the outward direction to the inward direction is limited by an outer edge, a bottom, and an inner edge. The screw part is assembled of a main piece and an insert piece. The main piece forms the outer edge, the inner edge is formed by the insert piece. The outer edge is limited by an outer wall surface, located on an outer circle, and by several internal projections, projecting from the outer circle towards the rotational axis up to a first circular line. The inner edge is limited by an inner wall surface, located on an inner circle and limited by several outer projections, projecting from the inner circle towards the exterior up to a second circular line. The first circular line is located completely within the second circular line. The diameter of the second circular line is larger than the diameter of the first circular line.

A threaded fastener, inserted into a hole in materials to be joined, receives a free-running collar (nut) with out-of-round duplex barrels. Spring-loaded twin sockets cradle the barrels and a restraining polygon key extends through the sockets and into a recess in the small face on the pin tail. Installation advances in tandem sequence; tightening before swaging. A machined groove with flat bottom and side rising at about 20 degrees from axial forms a boundary and partly reshapes crests from parallel to angular. Such inclination keeps the collar connected to the cavity of the larger of twin sockets throughout tangential tightening, rise of torque, displacement of crest material, recoil of the smaller socket on the end barrel, cessation of collar rotation and plunging torque. When recoil ends, radial torque on the smaller socket crushes and locks barrel material into underlying left hand helical troughs that interrupt the last few pin threads.

A bolt includes a head portion on which a recess is formed. The recess has a bottom surface and a sidewall extending from a periphery of the bottom surface. The sidewall has a lower end defined by the bottom surface and includes an increased diameter portion and a reduced diameter portion. The increased diameter portion has an inner diameter larger than an inner diameter of the lower end of the side wall. The reduced diameter portion has an inner diameter smaller than the inner diameter of the increased diameter portion. The reduced diameter portion is located opposite to the bottom surface across the increased diameter portion.

A self-feed bit system includes a shank extending along an axis and configured to be coupled to a tool holder of a power tool and a cutting head couplable to the shank and including a sector shaped base. A radially extending lip is at a leading edge of the sector shape facing in a cutting direction and includes a rake face facing the cutting direction at a rake angle relative to the axis. A radially extending cutting blade is coupled to the radially extending lip and extends axially forward from the base at a first height. An at least partially threaded tip is coupled to the shank and extends axially forward of the cutting blade. Two or more teeth are positioned on a perimeter of the base trailing the cutting blade. Each tooth extends axially forward from the base at a second height that is less than the first height.

A socket having an offset drive keyway for transmitting torque to asymmetric fastener heads to facilitate their rotation by applying torque across the fastener end to minimize stress on the fastener end-fastener shaft joint.