Patent ID: 8371787
Filing Date: 2013-02-12
Classification: F16B

Abstract:
1. A self-tapping screw comprising: a screw shaft formed of a cylindrical shaft that extends downward from a screw head and has a diameter that is constant over an entire length thereof; plural flights of constant-height external thread respectively having the same flight height formed at a part of the screw shaft extended right below the screw head; and plural flights of low-height external thread having flight height decreased gradually toward an end face of a shaft tip portion formed continuously with the constant-height external thread at the shaft tip portion of the screw shaft; wherein a slight arc face, having a curvature radius in a range of 0.2 to 0.6 mm, is formed continuously at respective connecting parts of upper and lower flanks with upper and lower root faces of the low-height external thread; wherein the slight arc face is formed so as to extend along a connecting part of a lower flank and a lower root face of a constant-height external thread end flight continuing to the low-height external thread; wherein the slight arc face is not formed at a connecting part of an upper flank and an upper rood face of the constant-height external thread end flight; and wherein the slight arc face is not formed at respective connecting parts of upper and lower flanks with upper and lower root faces of the flights of the constant height external thread other than the constant height external thread end flight.