of the present invention the harmonic drive gearing assembly 10 comprises a planar generally oval shaped wave generator cam plate 12 having a bore 14 for attachment to a drive shaft not shown the wave generator 12 has an outer periphery 18 with a bearing assembly 16 pressed thereabout the bearing assembly 16 consists of an inner race 20 an outer race 22 and a plurality of roller members 24 rotatively distributed therebetween a deformable flexspline 26 is disposed outwardly of and snugly engaged with the outer race 22 of the bearing assembly 16 a rigid fixed circular spline 28 is disposed radially outwardly of the deformable flexspline 26 an array of gear teeth 30 as shown in fig2 is arranged on the outer periphery of the flexspline 26 and another array of gear teeth 32 is arranged on the inner periphery of the circular spline 28 in a matable relationship therebetween the major axis of the wave generator 12 and the flexspline 26 is represented in fig2 at the 12 o 39 clock position 35 and likewise the minor axis in fig2 is at the 9 o 39 clock position 36 the maximum inclination of the teeth 30 of the flexspline 26 are found at the mid point 37 between the major and minor axes 35 and 36 referring now to fig3 and 4 the derivation of the curves defining the tooth profiles of the flexspline 26 and the circular spline 28 will now be explained in connection therewith fig3 depicts one tooth 60 of the flexspline 26 at a point of contact p 39 x 1 y 1 with the face 62a of a tooth.