, furnace or continuous furnace) and the differences between the charges of blank material, have a significant influence on the gear distortion. The distortions from heat treatment are critical to the final hard finishing operation. In addition to the blank body distortions, heat treating also causes a distortion of the individual teeth. The spiral angle changes, the flank length curvature is reduced and the pressure angle changes. To achieve the best results, you must pay attention to the processing and handling of the parts through the furnace. Quenching the ring gears with a quench press assures good flatness of the heat-treated ring gears. For instance, the hard finishing of bevel gears should provide a good surface finish and remove flank distortions.