Abstract: A process of forming molded bodies is provided in which precisely formed surfaces thereof have a precise interval therebetween. Such bodies are formed in a mold in which a first set of forming dies engage an interposed plastic mass of glass or the like, whereafter at least one auxiliary forming die enters the mold to engage and form the yet plastic mass. The first set of forming dies define critical surfaces and have a fixed interval therebetween following engagement with the plastic mass. The auxiliary die defines a non-critical surface on the body to be formed in the mold and enters the mold a distance determined by the mass of the plastic body.In a modified process of manufacture, the mold has an offset portion and is movable relative to the first forming dies whereby the mold cavity in which the plastic mass is disposed is reduced in volume and the desired body is formed having critical surfaces formed by the first forming dies.