The objects of this invention are achieved by a harmonic drive assembly comprised of a flexspline disposed within a rigid circular spline having opposed teeth in an extended contact arrangement, intermating at spaced apart locations corresponding to the eccentricities ofa rotatable oval shaped wave generator disposed within the flexspline, the rotation of which initiates relative motion between the flexspline and the circular spline due to a differing number of gear teeth between the flexspline and the circular spline. The tooth profiles of the flexspline and circular spline are determined, by a mapping curve which includes accommodation for tooth cant or inclination which occurs within the teeth of the flexspline as engagement with the teeth of the circular spline progresses