Synthesis of Geometric Primary Circles of Externally Meshed Skew-Axes Gears Available to Purchase

What are considered are geometric primary circles of gears which transform rotations between fixed skewed axes with a constant speed ratio. These imaginary circles differ from the pitch ones of the gears with parallel or intersecting axes. It seems they are used succeessfully for the first time as a start point in designing hyperbolic gears. Both the diameters and the mutual position parameters of the geometric primary circles are needed when gear over-alls and mounting distances as well as teeth geometry are determined.