Clinch nut

A self-clinching metal fastener for attachment to a plastically deformable metal member, said fastener including a body portion having a central axis and an axially extending pilot portion surrounding a central bore, said fastener having a transverse extent including an inner zone adjacent said bore and an outer zone adjacent said outer periphery of said fastener, wherein said inner zone has a generally cylindrical shape in said pilot portion and radially extends to provide said inner zone with a bulbous shape in said body portion, wherein the bulbous shape results in the outer zone having a varying radial thickness of increased hardness, said inner zone having an inner zone hardness and said outer zone having an outer zone hardness wherein at least a hardness of the outer zone is formed by a selective heat treatment, said outer zone hardness being greater than said inner zone hardness, said pilot portion including a first annular pilot end face extending around said bore and a second annular pilot end face extending around said first annular pilot end face, said first and second annular pilot end faces respectively having first and second pilot end face hardnesses, said second pilot end face hardness being greater than said first pilot end face hardness, said body portion including a top radial end face, said top radial end face having an annular top end face extending around said bore and having a hardness substantially equal to said inner zone hardness.