Topura Co., Ltd.

Nhk Spring Co., Ltd.

Naoki Horiuchi

Shigeto Mori

Mayumi Matsuno

Takeshi Suzuki

Noriyoshi Kaneda

Kouhei Miyamoto

Minoru Sugiyama

Keisuke Hibino

To provide a screw thread which achieves a further reduction in screwing torque while securing removability of a coating film or the like and which is capable of stabilizing conductivity. In a screw thread in which a recessed portion () is partially provided on a flank surface () of a screw thread ridge provided on a screw thread shaft main body (), a screw thread ridge () in a section where the recessed portion () is formed is smaller than a regular screw thread ridge (), and a ridge height (H) in a distal end portion in a screwing direction is lower than a ridge height (H) in a rear end portion in the screwing direction W.

Screw 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 (), a normal thread area (), a guide thread area () provided at a tip side of the shank portion with respect to the normal thread area () and in which a guide screw thread () is formed, and a rising area () in which a transition screw thread () gradually rising from the guide screw thread () to the complete screw thread () is formed. A tapered guide portion () is provided at a tip end side of the normal thread area () and includes at least the guide thread area (). The guide screw thread () is formed on an outer periphery of the tapered guide portion () which has a maximum diameter equal to or smaller than an inner diameter of an internal thread.

External thread member

An external screw member includes a parallel screw portion and a tapered screw portion provided on a side further toward a tip end than the parallel screw portion, and a plurality of sets of step portion and a transition screw thread portion are provided on at least one of the parallel screw portion and the tapered screw portion, the step portion having a reduced thread height in a radial direction and the transition screw thread portion gradually increasing in diameter from the step portion in an anti-driving rotation direction so as to reach a thread height of a normal screw thread portion. A top portion of the transition screw thread portion is positioned at an offset toward a pressure side relative to a position of a regular screw pitch in a minimum diameter portion of the step portion, and transitions to the regular screw pitch in the anti-driving rotation direction.

External screw member

An aluminum alloy contains 0.7% to 1.8% of silicon, 0.5% to 2.1% of copper, 0.4% to 1.8% of manganese, 0.6% to 1.6% of magnesium, and 0.1% to 0.7% of zinc in terms of mass ratio and the balance aluminum with inevitable impurities.

Aluminum alloy and fastener member

A tapping screw provides sufficient tightening force even if used with a thin screwed member and tightening target member. The tapping screw () includes a first ridge () and a second ridge () configured to have incomplete threads that are 180&#xb0; out of phase. The tapping screw () includes a first tightening force improvement ridge () and a second tightening force improvement ridge () that are set so as to be smaller than the outside diameters of complete thread sections of parallel threaded portions of the first ridge () and the second ridge () but larger than the inside diameter of the prepared hole are provided in each of areas which are 90&#xb0; out of phase with the first ridge () and the second ridge (), respectively, such that the tightening force improvement ridges bite into the prepared hole when the screw is fully screwed in.

Growing community of inventors

Kanagawa, Japan

Naoki Horiuchi