1. IN A METHOD OF CUTTING RECESSES IN THE WORKING FACES OF INTERNAL TEETH OF A TOOTHED MACHINE ELEMENT HAVING CIRCULARLY ARRANGED INTERNAL TEETH, ON BOTH SIDES OF EACH TOOTH, THE STEPS OF PROVIDING AN OSCILLATING BROACH UNIT HAVING ITS RADIUS OF OSCILLATION EQUAL TO THE RADIUS OF ARCUATE RECESSES, AND TWO BROACH CUTTERS SPACED AND SHAPED TO CUT SIMULTANEOUSLY RECESSES IN THE WORKING FACES OF TWO SPACED TEETH, THE FACES OF WHICH IN AN END VIEW ARE SUBSTANTIALLY PARALLEL TO A CORD OF THE GEAR CIRCLE, WHICH CORD IS SUBSTANTIALLY PARALLEL TO THE AXIS OF OSCILLATION OF THE BROACH, DISPOSING SAID BROACH UNIT WITHIN THE WORKPIECE TO HAVE ITS AXIS OF OSCILLATION COINCIDE WITH THE