Electroplated diamond milling tools are in general use for machining toroidal surfaces on plastic lenses. Diamond-impregnated metal-bonded tools, with a variety of grit sizes and concentrations, are universally used for milling optical glass. Research with electroplated diamond tools has demonstrated that an improved finish, consistant accuracy, faster cutting, with less power consumed, can be achieved when milling crown or flint glass using a smaller number of natural diamonds than are necessary for impregnated metalbonded tools.