Piercing and tapping screw with groove to facilitate tapping

Claim 1

A HOLE-PIERCING AND TAPPING SCREW FOR USE IN THIN SHEET METALS INCLUDING A HEAD AND A THREADED SHANK INTEGRAL THEREWITH HAVING AN UPPER HOLDING SECTION AND A LOWER ENTERING AND TAPPING SECTION, THE THREADS ON THE SHANK BEING V-SHAPED AND OF RELATIVELY COARSE PITCH AND THE THREAD CONVOLUTIONS ON SAID ENTERING SECTION DIMINISHING IN OUTSIDE DIAMETER BUT HAVING SHARP PERIPHERIES ALL THE WAY TO THE END TO FACILITATE ENTRANCE INTO AN UNTHREADED HOLE AND START THE TAPPING THEREOF, THE LOWER END OF SAID ENTERING AND TAPPING SECTION HAVING A METAL PIERCING TAPERED POINT AND HAVING AN ANNULAR GROOVE OF APPRECIABLE WIDTH AND DEPTH IN RELATION TO THE THICKNESS OF THE SHEET METAL TO BE PENETRATED PROVIDED THEREIN ABOVE THE METAL PIERCING TAPERED POINT AND IMMEDIATELY BELOW THE THREADS ON THE SHANK, SAID POINTED AND GROOVED LOWER END SECTION BEING RECESSED ON ONE SIDE TO DEFINE A SUBSTANTIALLY RIGHT ANGLE GROOVE, ONE SIDE OF WHICH IS IN THE DIAMETRICAL PLANE OF SAID LOWER END SECTION AND THE OTHER SIDE AT AN ACUTE ANGLE TO THE AXIS OF THE SCREW INCLINED IN THE SAME DIRECTION AS SAID THREADS, WHEREBY TO DEFINE A V-SHAPED PIERCING EDGE ON THE TAPERED POINT AND A REAMING EDGE ON THE PERIPHERY OF THE LOWER END SECTION WHICH LEADS IN THE SAME DIRECTION AS THAT IN WHICH THE