The invention relates to methods of stabilizing bone implants, including inserting a self-tapping implant having at least two helical grooves running in opposite directions around the implant.

The die forming process includes first passing a circular coarse thread cutter over the forming surface of the die at an angle away from parallel to a side edge matching a pitch for coarse threads to be formed by the die. The coarse thread cutter is truncated with a notch within a flattened tip, the notch forming upper portions of crests in the forming surface of the die. A fine thread cutter of circular form is then utilized to cut portions of the root of the dual threaded die. The fine thread cutter is angled relative to side edges of the die at an angle substantially half of an angle at which the coarse thread cutter is angled. The fine thread cutter cuts at a variable depth as the fine thread cutter advances along the root between the crests to form flanks of a bridge within the root.

The die forming process includes first passing a circular coarse thread cutter over the forming surface of the die at an angle away from parallel to a side edge matching a pitch for coarse threads to be formed by the die. The coarse thread cutter is truncated with a notch within a flattened tip, the notch forming upper portions of crests in the forming surface of the die. A fine thread cutter of circular form is then utilized to cut portions of the root of the dual threaded die. The fine thread cutter is angled relative to side edges of the die at an angle substantially half of an angle at which the coarse thread cutter is angled. The fine thread cutter cuts at a variable depth as the fine thread cutter advances along the root between the crests to form flanks of a bridge within the root.

A multi-station, reciprocating die pattern forming machine (500), including a pair of parallel reciprocal slide members (502, 503) with spaced pairs of pattern forming dies (504) thereon reciprocal between an insert position and an eject position. Drive mechanism (505, 506, 510) reciprocates the die pairs alternately between the insert position and eject position. Mechanism delivers and positions a pattern receiving blank (600) to a pair of dies when in the insert position. Axial translation of the dies causes the dies to rotate the blank at a center of process and impart a pattern upon the blank. Servo-motors on blank positioning mechanism provide feedback recognition of the position of the blanks during processing. The invention also relates to a method of patterning blanks.

A multi-station, reciprocating die pattern forming machine (500), including a pair of parallel reciprocal slide members (502, 503) with spaced pairs of pattern forming dies (504) thereon reciprocal between an insert position and an eject position. Drive mechanism (505, 506, 510) reciprocates the die pairs alternately between the insert position and eject position. Mechanism delivers and positions a pattern receiving blank (600) to a pair of dies when in the insert position. Axial translation of the dies causes the dies to rotate the blank at a center of process and impart a pattern upon the blank. Servo-motors on blank positioning mechanism provide feedback recognition of the position of the blanks during processing. The invention also relates to a method of patterning blanks.

A form-rolling die structure with die members which are pressed against a material to be threaded and which have rigid surfaces that are relatively displaced. The die members are equipped with a plurality of independent concave portions which form a substantially parallelogram shape when viewed from the normal of a virtual surface obtained by connecting the outermost portions of each of the rigid surfaces, and which are recessed from the virtual surface. Two of the corners at the sites corresponding to the four corners of the substantially parallelogram-shape of the concave portions are rounded. The periphery of each concave portion in the cross-section along the direction of the normal is rounded along the periphery of the substantially parallelogram shape. The concave portions form a substantially truncated-pyramid shape.

A form-rolling die structure with die members which are pressed against a material to be threaded and which have rigid surfaces that are relatively displaced. The die members are equipped with a plurality of independent concave portions which form a substantially parallelogram shape when viewed from the normal of a virtual surface obtained by connecting the outermost portions of each of the rigid surfaces, and which are recessed from the virtual surface. Two of the corners at the sites corresponding to the four corners of the substantially parallelogram-shape of the concave portions are rounded. The periphery of each concave portion in the cross-section along the direction of the normal is rounded along the periphery of the substantially parallelogram shape. The concave portions form a substantially truncated-pyramid shape.

A thread-rolling flat die for a threaded fastener, includes a thread-rolling surface including at least a bite surface to which a workpiece of the threaded fastener is supplied, a finishing surface formed adjacent to the bite surface, and a roll-off surface formed adjacent to the finishing surface. The bite surface includes at least: a first partial bite surface having an inclination and a second partial bite surface formed continuously from the first partial bite surface and having an inclination. A length L1 along a thread-rolling direction in the first partial bite surface, a length L3 along the thread-rolling direction in the finishing surface, a length L4 along the thread-rolling direction in the roll-off surface, and a diameter of a processed portion of the workpiece of the threaded fastener have a relationship of L1>L3>L4> the diameter of the processed portion.

A thread-rolling flat die for a threaded fastener, includes a thread-rolling surface including at least a bite surface to which a workpiece of the threaded fastener is supplied, a finishing surface formed adjacent to the bite surface, and a roll-off surface formed adjacent to the finishing surface. The bite surface includes at least: a first partial bite surface having an inclination and a second partial bite surface formed continuously from the first partial bite surface and having an inclination. A length L1 along a thread-rolling direction in the first partial bite surface, a length L3 along the thread-rolling direction in the finishing surface, a length L4 along the thread-rolling direction in the roll-off surface, and a diameter of a processed portion of the workpiece of the threaded fastener have a relationship of L1>L3>L4> the diameter of the processed portion.

The dual-threaded screw structure 1 has a first thread (S1) and a second thread (S2) with various leads formed on the dual-thread portion and has a function of preventing loosening without insufficiency in strength of the dual-thread portion. This dual-thread portion is composed of a first thread (S1) consisting of a coarse thread with a standard pitch P and a specific second thread (S2). The second thread (S2) is formed continuously on the thread ridge of the first thread (S1). The second thread (S2) has a sectional shape of this thread groove same as or substantially same as the first thread (S1), has a same twisting direction as the first thread (S1) and is a multi-threaded thread having threads with a triangular sectional shape and having a lead (L=n*P) a determined number (n)-times of a standard pitch P.