1. A GEAR SHAVING CUTTER ADAPTED TO CUT SUBSTANTIALLY EQUALLY AT OPPOSITE SIDES OF ITS TEETH WHEN ROTATED IN ONE DIRECTION IN TIGHT MESH WITH A WORK GEAR AT CROSSED AXES THEREWITH, SAID CUTTER BEING IN THE FORM OF A HELICAL GEAR HAVING TEETH THE FLANKS OF WHICH ARE PROVIDED WITH A PLURALITY OF PARALLEL GROOVES, THE SIDE WALLS OF SAID GROOVES INTERSECTING THE FLANK SURFACES OF SAID TEETH TO FORM SHARP CUTTING EDGES, EACH GROOVE EXTENDING LONGITUDINALLY IN A DIRECTION SUCH THAT THE CUTTING EDGES FORMED BY THE INTERSECTION OF ITS SIDE WALLS WITH THE FLANKS OF THE TEETH EXTEND IN PLANES OF ROTATION OF THE CUTTER PERPENDICULAR TO ITS AXIS, THE SIDE WALLS OF SAID GROOVES BEING DISPOSED SUCH THAT ALL OF THE CUTTING EDGES, BOTH AT OPPOSITE SIDES OF SAID TEETH HAVE SUBSTANTIALLY EQUAL INCLUDED ANGLES OF NOT LESS GROOVES AND AT OPPOSITE SIDES OF SAID TEETH HAVE SUBSTANTIALLY EQUAL INCLUDED ANGLES OF NOT LESS THAN 90 DEGREES.