There is provided a seizure prevention bolt capable of preventing seizure caused by oblique insertion as well as seizure caused by invasion of a foreign matter such as a spatter. An incomplete screw portion having an outer diameter d that is larger than an inner diameter D.sub.1 of a female screw and smaller than (D+D.sub.1)/2 is formed at a front end of a normal screw portion formed in a bolt shaft over one or more pitches, and a vertical groove for cutting out a foreign matter such as a spatter is formed in the incomplete screw portion. D in the above expression is a nominal diameter of the bolt.

A bone screw includes a receiving sleeve having a sleeve wall which forms a seat for a longitudinal support for the surgical connection of adjacent bone screws. The bone screw includes an internal thread. A thread turn of the internal thread has a widened lead-in region on the thread lead-in side.

A method for correcting translational misalignment between male and female fastener members to prevent false threading, the method comprising: inserting a lead end of a male fastener member into a female fastener member, wherein the female fastener member comprises: at least one female fastening thread formed in an interior of the female fastener member, at least one female lead thread formed in the interior of the female fastener member, the at least one female lead thread having a groove in the crest, and wherein the male fastener member comprises: a shank that has a lead end for insertion into the interior of the female fastener member; at least one male fastening thread formed on the exterior of the shank as a plurality of thread windings adapted to mate with the at least one female fastening thread; at least one male lead thread formed on the exterior of the shank at the lead end that is at least a half winding around the shank and comprises a curved profile defined by an arc having a radius approximately equal to a radius of an arc that is tangent to both flanks of a thread profile of the at least one male fastening thread and below the pitch line of the at least one male fastening thread; and rotating the fastener members relative to each other while the at least one male lead thread of the male fastener member passes over and does not thread into the groove in the crest of the at least one female lead thread of the female fastener member.

An anti-false threading fastener system comprising: a female fastener member comprising: at least one female fastening thread formed in an interior of the female fastener member; at least one female lead thread formed in the interior of the female fastener member; a male fastener member comprising: a shank that has a lead end for insertion into the interior of the female fastener member; at least one male fastening thread formed on the exterior of the shank as a plurality of thread windings adapted to mate with the female fastening thread; at least one male lead thread formed on the exterior of the shank at the lead end that is at least a half winding around the shank and comprises a curved profile defined by an arc having a radius approximately equal to a radius of an arc that is tangent to both flanks of a thread profile of the at least one male fastening thread and below the pitch line of the at least one male fastening thread.

A male anti-false thread fastener member having features, including: a shank that has a lead end and a tool engagement end; a head formed at the tool engagement end of the shank; at least one male fastening thread formed on the exterior of the shank as a plurality of thread windings adapted to mate with a corresponding female fastening thread formed in an interior of a female fastener member; at least one male lead thread formed on the exterior of the shank at the lead end that is at least a half winding around the shank and comprises curved profile defined by an arc having a radius approximately equal to a radius of an arc that is tangent to both flanks of a thread profile of the at least one male fastening thread and below the pitch line of the at least one male fastener thread.

A male anti-cross threading fastener comprising: a substantially round shank having a lead end, a torque end, and a plurality of male threads around a circumference of the shank, the plurality of male threads comprising: a standard thread around at least a portion of the circumference of the shank and having a standard thread contour, wherein a width and a thread angle of the standard thread enables engagement with corresponding female threads, wherein the major diameter of the standard thread is between a lower major diameter limit and a higher major diameter limit; a transitional thread around at least a portion of the circumference of the shank and having a transitional thread contour with a width and a thread angle similar to the width and thread angle of the standard thread that enables engagement with corresponding female threads; an anti-cross thread around at least a portion of the circumference of the shank and having an anti-cross thread contour and an outside diameter configured to promote alignment of the male anti-cross thread fastener with a female fastener; and a lead thread around at least a portion of the circumference of the shank and having a lead thread contour, and wherein the transitional thread contour has a height that transitions from the lower major diameter limit of the standard thread to the outside diameter of the anti-cross thread.

A threaded closure system includes a threaded opening and a threaded closure, where at least one thread of the threaded opening or the threaded closure has a leading portion with a steeper angle than the rest of the thread.

A male anti-cross threading fastener comprising: a substantially round shank having a lead end, a torque end, and a plurality of male threads around a circumference of the shank, the plurality of male threads comprising: a standard thread around at least a portion of the circumference of the shank and having a standard thread contour, wherein a width and a thread angle of the standard thread enables engagement with corresponding female threads, wherein the major diameter of the standard thread is between a lower major diameter limit and a higher major diameter limit; a transitional thread around at least a portion of the circumference of the shank and having a transitional thread contour with a width and a thread angle similar to the width and thread angle of the standard thread that enables engagement with corresponding female threads; an anti-cross thread around at least a portion of the circumference of the shank and having an anti-cross thread contour and an outside diameter configured to promote alignment of the male anti-cross thread fastener with a female fastener; and a lead thread around at least a portion of the circumference of the shank and having a lead thread contour, and wherein the transitional thread contour has a height that transitions from the lower major diameter limit of the standard thread to the outside diameter of the anti-cross thread.