US Patent 8342788 Chiplessly thread-forming screw

A chiplessly thread-forming screw has a stem (11) at one end of which a tip (13) is provided and at another end of which a head (14) is provided, and which has a pointed conical section (21) extending from the tip (13) in a direction of the head (14), a cylindrical section (25) arranged between the first pointed section (21) and the head (14), a first cambered section (22) adjoining the pointed conical section (21) in the direction of the head, and a second cambered section (24) arranged between the first cambered section (22) and the cylindrical section (25) and an outer surface (16) of which has a second curvature radius (R2) unequal to the first curvature radius (R1) of the outer surface (12) of the first cambered section (21).