Abstract: A self-clinching fastener of the type for connection to a workpiece comprising sheet material, includes a head and a shank, with a groove formed in the shank, with the head being embeddable in the sheet material to displace material thereof into the groove to form a mechanical interlock between the material of the sheet material and the fastener. The head includes a plurality of radially disposed projections extending axially outwardly of an undersurface thereof and intermediate the undersurface and the groove. These projections each include an axially facing recess therein, such that the material of the workpiece being displaced will flow into the groove and the recesses in the projections, to lock the fastener to the workpiece. The shank may also include an extruding portion to resize an aperture in the sheet material, prior to the deforming of said sheet material by said head.