High precision machining provides an extended fabrication capability for optical parts having geometries heretofore prohibitively expensive to achieve. The conventional optical fabrication process of "cut and try" makes complex optical parts exponentially more time consuming than simple flats and spheres and, therefore, expensive; yet a numerical control machine tool can cut complex contours easily. Combining this geometric capability of the numerical control machine tool with high precision machining technology makes possible a form accuracy and finish of optical quality. Moreover, the machining process allows added features such as mounting flanges and fittings to be designed as an integral part of the optical part usually not possible to accommodate on optical grinding and polishing machines. This means that the part can be held during the fabrication process as it will be held in the final assembly, reducing the changes of distortion that might otherwise occur during assembly.