"Using illustrations this paper explains that bias error (""the twisted tooth phoneme"") is a by-product of applying conventional radial crowning methods to produced crowned leads on helical gears. The methods considered are gears that are finished@ shaped@ shaved@ form and generated ground. The paper explains why bias error occurs in these methods@ and then addresses what techniques are used to limit/eliminate bias error. Profile and lead inspection charts will be used to detail bias error and the ability to eliminate it. The paper details the simultaneous interpolation of multiple axes in the gear manufacturing machine to achieve the elimination of bias error. It also explains that CNC machine software can be used to predict bias error@ and equally important that it could be used to create an ""engineered bias correction"" to increase the load carrying capacity of an existing gear set."