Fastener for attachment to metallic structures

Claim 1

A fastener having a penetrating portion for driving into metallic structures comprising a shank, a hardened penetrating portion at one end of said shank, said penetrating portion including a substantially frusto-conical tip having a penetrating point at one end and a predetermined diameter at the opposite end, a reduced neck formed at said opposite end of said tip defining an annular groove having a cross-sectional width substantially greater than the depth, the opposed ends of said neck being of substantially the same diameter, an enlargement connected to said neck and defining a first substantially radial shoulder extending outwardly therefrom for engaging the metallic structure and causing the metal thereof to flow into said annular groove and form a mechanical lock, said enlargement terminating in a second substantially radial shoulder of greater diameter than said first shoulder at said one end of said shank to stop penetration of said penetrating portion into the metallic structure, said enlargement being of a volume at least as great as and approximating the volume of said annular groove to cause the flowing metal to fill said annular groove as said second shoulder stops penetration of said penetrating portion, whereby the penetrating portion of said fastener may be driven into the metallic structure and said first shoulder causes the metal of the metallic structure to flow into the area adjacent to said neck and form a mechanical lock therewith and said second shoulder stops penetration of said penetrating portion into the metallic structure.