| 主权项 |
1. A hole-forming and thread-forming screw with a screw head that has a screw-driving formation for rotational driving by a screwdriver or tool at high speed, a screw shaft that has a threaded groove section and a hole-forming section extending from the threaded groove section and having a thread-free portion extending towards a thread free screw tip, wherein a transverse cross-section of the hole-forming section continuously decreases as it extends from a full diameter of the screw shaft in a direction towards the screw tip, further wherein the hole-forming section includes a first sideline section having a first curvature, a second sideline section having a second curvature different from the first curvature, and an indenture formed by the transition from the first curvature to the second curvature, wherein the first and second sideline sections are directly adjacent to each other;
wherein the screw shaft has a threaded edge inscribed along the threaded groove section of the screw shaft, the threaded groove section extending to the hole-forming section of the screw shaft, the threaded groove section and the threaded edge having a transverse cross-section in a form of a polygon, particularly a triangle with rounded corners and convex curved sides; and wherein the screw shaft has a holding section extending towards the screw head, wherein the threaded groove section extends from the holding section to the hole-forming section, and wherein the transverse cross-section of the screw shaft in the holding section is formed to be closer to circular than the polygonal cross-section of the threaded groove section. |
