In 1975 the State Standard Institute confirmed as the State special standard of the unit of length for an evolvent surface a complex of means of measurement developed at the KhGNIIM. The design of this standard and the realization of a plan for the introduction of the standard and an All-Union checking scheme ensured unity of the measurements of the parameters of gear wheels [i]. The special standard covered a range of radii of the fundamental circles of the evolvents from 37 mm to 150 mm, corresponding mainly to gear wheels of average modulus. At the present time, as a result of the development of accurate instrument construction, smallmodulus gear trains have become of special importance. To broaden the limits of the State special standard in this region a working standard of the unit of length has been developed at the KhGNIIM for evolvent surfaces of small-modulus gear wheels with ro = 10-60 mm.