A threaded fastener system, incorporating a bolt and a nut assembly, wherein the bolt has a threaded lead entry point whose pitch and helix angle are of a higher magnitude than that of those on the body/shank of the bolt.

A fastening tool according to the invention includes: a female screw member (10) having an inverse screw that is fixed to the first member (1); a collar bolt (11) that is screwed with the female screw member (10); a fastening bolt (27) that is inserted into a center hole (19) of the collar bolt (11) from the second member side (2) and rotates the collar bolt (11) through a torque transmitter (25), thereby moving the collar bolt to a position colliding with the second member (2); and a fastening nut (33) that is fixed to the first member (1). An earth claw (21) protruding toward the second member (2) is formed at an outer periphery of an end surface of the collar bolt (11) facing the second member. The earth claw (21) is configured to bite into the second member (2) in an axial direction due to axial force generated by screwing the fastening bolt (7) with the fastening nut (33), thereby breaking an insulating coating layer (3) and thus ensuring electrical conduction.

A nut is configured to be secured to a bolt. The nut includes a main body that defines an axially aligned bore with threads disposed on an inner wall thereof. Further, the nut includes a dome-shaped head that has an axially aligned aperture and that is provided to be deformed by threads on the bolt when a predetermined burst-through torque is applied thereto.

A bolt which can prevent seizure is provided due to the bolt being installed obliquely. A guide portion is formed between a groove portion formed at a distal end portion of the threaded portion and a surface end position on a base end side of the tapered surface, a starting end portion of the guide portion being an intersection between the surface end position on the base end side of the tapered surface and a helix according to the groove portion, a terminal end portion of the guide portion overlaps with the distal end portion of the threaded portion, an angle in the direction around the axis of the bolt from the starting end portion to the terminal end portion is set in the range of 90° to 360°.

The objective is to provide a bolt which can more effectively suppress occurrence of seizure due to both oblique insertion and biting of foreign substances. The bolt includes a tapered surface, a guide portion, and a threaded portion in order from a distal end side and further includes a plurality of recesses provided on the tapered surface and a plurality of cutout portions provided at a distal end portion of the threaded portion.

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.

An external thread member capable of preventing oblique entry or insertion by a short screw tip shape is provided including, in its shank portion (20), a normal thread area (22), a guide thread area (24) provided at a tip side of the shank portion with respect to the normal thread area (22) and in which a guide screw thread (23) is formed, and a rising area (26) in which a transition screw thread (25) gradually rising from the guide screw thread (23) to the complete screw thread (21) is formed. A tapered guide portion (30) is provided at a tip end side of the normal thread area (22) and includes at least the guide thread area (24). The guide screw thread (23) is formed on an outer periphery of the tapered guide portion (30) which has a maximum diameter equal to or smaller than an inner diameter of an internal thread.

An external thread member capable of preventing oblique entry or insertion by a short screw tip shape is provided including, in its shank portion (20), a normal thread area (22), a guide thread area (24) provided at a tip side of the shank portion with respect to the normal thread area (22) and in which a guide screw thread (23) is formed, and a rising area (26) in which a transition screw thread (25) gradually rising from the guide screw thread (23) to the complete screw thread (21) is formed. A tapered guide portion (30) is provided at a tip end side of the normal thread area (22) and includes at least the guide thread area (24). The guide screw thread (23) is formed on an outer periphery of the tapered guide portion (30) which has a maximum diameter equal to or smaller than an inner diameter of an internal 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.