1. A METHOD FOR PRODUCING AN INTERNAL HELICAL THREAD CONVOLUTION HAVING PORTIONS OF DIFFERENT FLANK WIDTHS ON A SIDE WALL OF A THROUGH OPENING IN A METAL BODY COMPRISING THE STEPS OF TAPPING THE SIDE WALL OF SAID OPENING IN SAID METAL BODY WITH A LEADING SECTION OF A TAP BY RELATIVELY ROTATING SAID TAP AND SAID METAL BODY TO FORM A SCREW THREAD CONVOLUTION HAVING A GIVEN FLANK WIDTH AND UTILIZING SAID LEADING TAP SECTION AS A LEAD SCREW FOR LEADING SAID METAL BODY ONTO AN AXIALLY SPACED FOLLOWING TAP SECTION, TAPPING SAID THREAD CONVOLUTION FORMED BY SAID LEADING TAP SECTION WITH SAID FOLLOWING TAP SECTION TO DECREASE THE FLANK WIDTH THEREOF UNTIL SAID METAL BODY DISENGAGES SAID LEADING TAP SECTION WHEREUPON SAID LEADING TAP SECTION NO LONGER PROVIDES A LEAD SCREW ACTION AND SAID FOLLOWING TAP SECTION AND SAID METAL BODY SHIFT AXIALLY RELATIVE TO EACH OTHER SO THAT THE FOLLOWING TAP SECTION NO LONGER DECREASES THE FLANK WIDTH OF THE REMAINING PORTION OF THE THREAD CONVOLUTION FORMED BY SAID LEADING TAP SECTION, AND CONTINUING SAID RELATIVE ROTATION BETWEEN SAID TAP AND METAL BODY WITH SAID REMAINING PORTION OF THE THREAD CONVOLUTION PASSING FREELY OVER THE FOLLOWING SECTION OF THE TAP.

11. A TAP FOR PRODUCING AN INTERNAL HELICAL SCREW THREAD CONVOLUTION HAVING FIRST AND SECOND PORTIONS OF DIFFERENT FLANK WIDTHS ON THE SIDE WALL OF A THROUGH OPENING IN A METAL BODY COMPRISING: A TAP BODY HAVING LEADING AND FOLLOWING TAP SECTIONS AND A FORWARD END FOR RECEIVING THE METAL BODY AND A REARWARD END FOR REMOVAL OF THE METAL BODY, FIRST THREAD CUTTING MEANS ON SAID LEADING TAP SECTION FOR CUTTING A HELICAL THREAD CONVOLUTION ON THE SIDE WALL OF SAID OPENING HAVING A GIVEN FLANK WIDTH, SECOND THREAD CUTTING MEANS ON SAID FOLLOWING TAP SECTION WHICH IS EFFECTIVE TO REMOVE METAL FROM ONE OF THE FLANKS OF THE SCREW THREAD CONVOLUTION FORMED BY THE LEADING TAP SECTION FOR A PORTION OF THE AXIAL LENGTH THEREOF TO DECREASE THE FLANK WIDTH THEREOF TO FORM SAID FIRST PORTION AND TO PASS FREELY THROUGH THE REMAINING PORTION OF SAID THREAD CONVOLUTION FORMED BY SAID LEADING SECTION.