Fastener and electrode therefor

Claim 1

IN A SELF-LOCATING WELD NUT ADAPTED TO REST IN A WELDING POSITION WITHIN A WELDING HEAD HAVING A TAPERED OUTWARDLY DIVERGING CONCAVE PORTION AND IN ALIGNMENT ON AN APERTURED SUBSTANTIALLY PLANAR WORK PIECE TO WHICH IT IS TO BE SECURED AND WHICH WORK PIECE IS SUPPORTED AND ALIGNED ON AN OPPOSED WELDING HEAD; A NUT BODY PROVIDED WITH A PAIR OF OPPOSITE TOP AND BOTTOM END FACES, WITH CONNECTING SIDE FACES PERPENDICULAR TO SAID END FACES, AND WITH A THREAD BORE; SAID TOP AND BOTTOM END FACES HAVING RELATIVELY PLANAR MAJOR FACE AREAS ABOUT SAID THREAD BORE, SAID THREAD BORE DEFINING A CENTRAL AXIS EXTENDING THROUGH SAID NUT BODY BETWEEN SAID END FACES, SPACED-APART INTEGRAL WELD PROJECTIONS EXTENDING FROM SAID BOTTOM END FACE ADJACENT SAID SIDE FACES TO POSITION SAID NUT BODY ON THE WORK PIECE, SAID TOP END FACE HAVING PORTIONS SLOPING RADIALLY-OUTWARDLY FROM ITS SAID PLANAR FACE AREA AND WITH RESPECT TO AND REMOTELY OF THE THREAD BORE AND DOWNWARDLY BELOW SAID PLANAR FACE AREA INTO SAID SIDE FACES IN SUBSTANTIALLY OPPOSED CENTRAL ALIGNMENT WITH SAID WELD PROJECTIONS FOR DEFINING A TAPERED CONVEX TOP PORTION TO FIT IN AN ADJUSTABLY-CENTERING SUBSTANTIALLY COMPLEMENTARY MANNER WITHIN THE TAPERED CONCAVE PORTION OF THE FIRST-MENTIONED WELDING HEAD, AND SAID CONVEX TOP PORTION BEING SUBSTANTIALLY SYMMETRICAL WITH A SURFACE OF REVOLUTION OF THE AXIS OF THE THREAD BORE AND BEING TANGENT TO A COAXIAL CONICAL SURFACE OF PROJECTION HAVING AN APEX ANGLE OF 70* TO 100*.