Abstract: A milling cutter rotatable about an axis and including a cylindrical steel core having helical tapered threads, such as V-shaped threads, diamond grit of a suitable mesh being appropriately secured, as by nickel plating, onto the crests, roots and flanks of the threads, the diamonds being substantially contiguous one another and so related to each other that as the cutter rotates against the work, the individual crest diamonds will first cut the work and eventually break off. Because of the helical pattern, the cutting action will continue, since one of the other diamonds lying in the same transverse plane normal to the axis as the missing diamond will operate upon the work being cut. The loss of the outermost or crest diamonds will expose diamonds in the tapered flanks of the thread to provide cutting points on the cylinder that are operable to cut the work, the flank diamonds traversing the same path normal to the axis of the cutter as the crest diamonds.