Patent ID: 7179036

Claim:
A fastening arrangement, comprising: a thread-forming lobular screw having a shaft and a head joined to a proximal end of the shaft, a thread being formed on an outer surface of the shaft, the thread defining a major or diameter at a crest of the thread and a minor diameter at a root of the thread, the shaft defining a plurality N of lobes circumferentially spaced about a central longitudinal axis of the shaft, the major and minor diameters each reaching a local maximum at each of the lobes and diminishing between the lobes; and a member having a hardness at least as great as that of the screw and defining a non-tapped pilot hole therein, the pilot hole comprising a central portion having a diameter intermediate the major and minor diameters of the lobes, and a plurality N of circumferentially spaced cutouts extending radially out from the central portion, the pilot hole defining a plurality of longitudinal edges generally parallel to the axis of the screw shaft at junctures between the cutouts and central portion of the pilot hole, whereby turning of the screw in the pilot hole causes the thread on the lobes to plastically deform the member beginning at the longitudinal edges so as to form a thread in the pilot hole.