an improved tool in the form of a tooth forming rack for cold working a cylindrical workpiece to form teeth thereon to produce , for example , a toothed gear is provided . the rack comprises a plurality of releasable inserts mounted on a tool holder . the inserts are of the throw - away type which enables replacement of only that portion of the rack that is worn or broken , thus extending the ueful life of the entire rack . in a first embodiment the inserts are releasably attached to the tool holder by threaded capscrews . in an alternate embodiment a milled slot within the inserts permits retention by means of tapered retainers attached to the tool holder by threaded capscrews .