Cold-formed self-piercing nut

Claim 1

A SELF-PIERCING AND CLINCHING NUT ADAPTED TO BE FLUSH-MOUNTED THROUGH A METAL PANEL, COMPRISING, A POLYGONAL BLANK NON-DEFORMABLE DURING APPLICATION TO SAID PANEL AND HAVING A REAR FACE AND AN OPPOSITE FRONT ATTACHING FACE AND PROVIDED WITH AN AXIAL BORE, SAID ATTACHING FACE INCLUDING A BEARING SURFACE ADJACENT THE PERIPHERY THEREOF AND A CIRCULAR PIERCING EDGE SPACED RADIALLY INWARDLY OF SAID SURFACE, AN AXIALLY EXTENDING CIRCULAR RECESS WITHIN SAID ATTACHING FACE BETWEEN SAID PIERCING EDGE AND BEARING SURFACE, SAID PIERCING EDGE AXIALLY EXTENDING OUTWARDLY BEYOND THE PLANE OF SAID BEARING SURFACE, SAID CIRCULAR RECESS INCLUDING AN UNDERCUT PORTION HAVING A DIAMETER LESS THAN THE DIAMETER OF SAID PIERCING EDGE, SAID UNDERCUT PORTION EXTENDING RADIALLY INWARDLY IN AN AXIAL DIRECTION FROM SAID PIERCING EDGE TO A POINT WITHIN SAID BLANK BEYOND THE PLANE OF SAID BEARING SURFACE, AND A PLURALITY OF RADIAL LOCKING RIBS IN SAID RECESS EXTENDING INWARDLY FROM SAID BEARING SURFACE TO A POINT SHORT OF SAID UNDERCUT PORTION, EACH RIB INCLUDING A FLAT TOP SURFACE AND A PAIR OF SIDE WALLS DIVERGING THEREFROM TOWARDS THE BASE OF SAID RECESS.