Abstract: A mold-forming cup has a frustoconical interior tapering in cross-sectional size from the top of the cup to the bottom. A metal master model is mounted generally centrally of the interior of the cup, whereupon the cup is packed with rubber mold material. The mold material is vulcanized and the resulting mold is cut into top and bottom sections such that the master model can be removed. The mold sections are placed back together and inserted into a retaining ring having a frustoconical interior of a size slightly smaller than the size of the interior of the mold-forming cup to accommodate for shrinkage of the mold during vulcanization. The mold is held in the retaining ring under pressure so as to be restrained on all sides during injection of wax into the central cavity of the mold to form a wax pattern of the same shape as the master model.