Self-tapping screw

Claim 1

A SELF-TAPERING SCREW ADAPTED TO FASTEN TOGETHER TWO THIN METAL SHEETS EACH PROVIDED WITH A MARGINAL PORTION SURROUNDING A HOLE FOR PASSAGE OF THE SCREW, SAID SCREW COMPRISING AN INTEGRAL HEAD AND SHANK, THE UNDERSIDE OF THE HEAD HAVING AN ANNULAR BEARING AREA AND AN ANNULAR RECESS BETWEEN THAT AREA OF THE SHANK, A FULL FORMED THREAD ON THE SHANK TERMINATING SUBSTANTIALLY AT THE TRANSVERSE PLANE DEFINED BY SAID BEARING AREA, THE UNTHREADED SHANK PORTION EXTENDING BETWEEN THE TERMINAL END OF THE THREAD AND THE BOTTOM OF THE RECESS BEING SUBSTANTIALLY CYLINDRICAL AND HAVING A DIAMETER LESS THAN THE CREST DIAMETER OF THE THREAD BUT GREATER THAN THE ROOT DIAMETER OF THE THREAD AND SUBSTANTIALLY EQUAL TO THE PITCH DIAMETER THEREOF, THE THREAD BEING CAPABLE OF DEFORMING THE MARGINAL PORTION OF AT LEAST THE TOP ONE OF THE SHEETS TO PROVIDE A LEADING EDGE THEREIN AS THE SCREW IS THREADED INTO THE SHEETS AND THE TERMINAL PORTION OF THE THREAD ON CONTINUED ROTATION OF THE SCREW BEING CAPABLE OF EXTRUDING THE ENTIRE MARGINAL PORTION OF AT LEAST THE TOP SHEET COMPLETELY INTO THE RECESS UNDER THE HEAD AND TO ELIMINATE THE LEAD PREVIOUSLY PRODUCED ON THE EDGE THEREOF, THEREBY TO CAPTURE AT LEAST THE TOP SHEET WITH ITS MARGINAL PORTION WHOLLY CONFINED BETWEEN THE BOTTOM OF THE RECESS AND THE ADJACENT TERMINAL END OF THE THREAD OF THE SHANK.