A METHOD OF HEAT-TREATING AND HARDENING A STEEL PRODUCT SUCH AS A TOOTHED WHEEL AND SIMILAR STRUCTURAL ELEMENTS, REQUIRING A HARDNESS AND ABRASION RESISTANCE ON PORTIONS OF ITS WORKING SURFACES INCREASED IN COMPARISON TO THE HARDNESS AND ABRASION RESISTANCE OF THE REMAINING PORTIONS COMPRISING THE STEPS OF PROVIDING ON THE SURFACE OF SAID PRODUCT AT LEAST ONE GROOVE SEPARATING THE SAID SURFACES OF PORTIONS OF REQUIRED INCREASED HARDNESS FROM THE REMAINING SURFACES; LOCALLY HEAT-TREATING THE SAID PORTIONS OF THE SURFACES REQUIRING AN INCREASED HARDNESS AS THEY ARE DIVIDED BY SAID AT LEAST ONE GROOVE AND SUBSEQUENTLY HARDENING BY QUENCHING THE HEAT-TREATED PORTIONS LEAVING THE REMAINING PORTIONS WITH ITS ORIGINAL HARDNESS AND ABRASION RESISTANCE.