The Figure shows according to studies by Glaubitz [1] according to the FZG-tension test according to DIN 51354, how much depends on the specific wear of the Rockwell surface hardness HRC of the teeth. In good quality gears so all gears-chrome-manganese steel and hardened in use at 60 to 62 HRC. In comparison to the hardened wheels of the relatively soft and tough core and a better resistance against Stoßbeanspruehung favorable internal attenuation of noise excitations.