Abstract: A soluble wax core insert to be used in making a wax replica of a hollow metal jewelry ring has an inner round radius design and an arcuate portion having an arcuate extent of at least 140.degree.. The soluble wax core insert is formed by molding in a metal mold. Once formed, the core insert is placed in another metal mold and a plastiwax is introduced into and fills a cavity around the core insert. The plastiwax hardens and is removed from the latter mold with the core insert embedded in the hardened plastiwax article. The wax core insert is removed from the plastiwax article to yield a wax replica of the metal ring to be produced. The wax replica has an inner round radius design and is used to form a mold cavity in an investment material, which is used to cast the hollow metal jewelry ring.