The present invention provides a looseness-prevention screw thread structure including a screw thread having a predetermined pitch, a no-load flank which is an inclined surface in a direction in which the screw thread is advanced, and a load flank which is an inclined surface in a direction in which the screw thread is retracted, the no-load flank and the load flank being formed at both sides of the screw thread, in which the no-load flank of the screw thread includes: a first tangential portion which abuts against an arc portion formed at a thread crest of an opposing fastening object; and a second tangential portion which has a preset angle with respect to the first tangential portion and abuts against the arc portion.

A wood screw, having a shaft, a screw tip, and thread turns. The thread turns run circumferentially on at least a portion of the shaft, preferably through or into a screw tip. The wood screw includes at least one arc-shaped protrusion between at least two adjoining ones of the thread turns.

A bolt includes a head portion and a shaft portion. The shaft portion includes an ordinary screw portion that meshes with a nut, and a guide screw portion that is provided on a distal end side of the ordinary screw portion and has a screw thread having a diameter smaller than that of a screw thread of the ordinary screw portion. A protective portion having a diameter larger than a minor diameter of the ordinary screw portion is formed continuously from the guide screw portion at a distal end of the guide screw portion. A pressure flank surface is formed at a distal end of the screw thread of the guide screw portion, but a clearance flank surface is not formed thereat.

A bolt includes a head portion and a shaft portion. The shaft portion includes an ordinary screw portion that meshes with a nut, and a guide screw portion that is provided on a distal end side of the ordinary screw portion and has a screw thread having a diameter smaller than that of a screw thread of the ordinary screw portion. A protective portion having a diameter larger than a minor diameter of the ordinary screw portion is formed continuously from the guide screw portion at a distal end of the guide screw portion. A pressure flank surface is formed at a distal end of the screw thread of the guide screw portion, but a clearance flank surface is not formed thereat.

A method and system for increasing damping capacity in a mechanical fastener by utilizing dry friction between individual wires of a sheathed rope is disclosed. For metal fasteners, the sheathed rope is inserted loosely into a thick-walled metal tube. The tube is then rolled to reduce the tube diameter, thereby uniformly embedding the rope into the tube material. The tube is then subjected to either cold or hot forming. After forming, the fastener blank may be threaded. For composite or plastic fasteners, the sheathed rope includes insert locators attached to the sheathing. The sheathed rope having the insert locators is placed in the mold cavity prior to the polymerizable material being injected into the mold. Regardless of the embodiment, the resulting fastener has increased damping due to the dry inter-wire friction within the embedded rope which develops between the surfaces of individual wires upon dynamic loading of a fastened joint.

A method and system for increasing damping capacity in a mechanical fastener by utilizing dry friction between individual wires of a sheathed rope is disclosed. For metal fasteners, the sheathed rope is inserted loosely into a thick-walled metal tube. The tube is then rolled to reduce the tube diameter, thereby uniformly embedding the rope into the tube material. The tube is then subjected to either cold or hot forming. After forming, the fastener blank may be threaded. For composite or plastic fasteners, the sheathed rope includes insert locators attached to the sheathing. The sheathed rope having the insert locators is placed in the mold cavity prior to the polymerizable material being injected into the mold. Regardless of the embodiment, the resulting fastener has increased damping due to the dry inter-wire friction within the embedded rope which develops between the surfaces of individual wires upon dynamic loading of a fastened joint.

Cold-forming equipment configured as a high precision thread rolling assembly utilizing racks, guide rails, a bearing assembly including rolling element linear motion bearings and a gear reduction assembly.

Cold-forming equipment configured as a high precision thread rolling assembly utilizing racks, guide rails, a bearing assembly including rolling element linear motion bearings and a gear reduction assembly.

A die matching system which is preferably implemented in die rolling machinery for fasteners employs witness or reference marks on each of the dies. An eddy current sensor is employed to sense the witness marks and to detect change in the relative position of the witness mark and hence the position of the rotatable dies. The change in position is then processed and a signal is transmitted to servo motors to change the relative position of the dies to compensate for the position changes continuously during the operation of the die rolling machinery. In one preferred form, the witness mark is in the form of a recess milled into the bottom end surface of the cylindrical die.

A rack bar blank for a steering system is provided. The rack bar blank includes a first region having a circular cross-section. The rack bar blank also includes a second region having a flattened surface along a length thereof, the flattened surface present prior to formation of teeth.