Abstract: A modular unscrewing injection mold and core assembly therefor includes a mold base, a core receiving opening extending through the mold base, the core assembly being removably mounted in the core receiving opening and including first and second core shells that may be secured together to receive a rotating core therebetween; a mold core rotatably mounted between the shells; a pinion gear formed on the mold core for being driven by a rack in the mold base, for rotating the mold core; the core assembly being releasably secured in the base.