Abstract: A method is disclosed for producing cast metal parts having smooth surfaces held to close dimensional tolerances, eliminating the need for machining. The method includes making a core box and pattern to closer tolerances than the finished part, producing a sample core and mold using sand of predetermined characteristics under regulated conditions. The sample core is precisely assembled with the sample mold and gauged. Thereafter, a prototype part is cast at a controlled temperature and cooled for a controlled time. The dimensions of the prototype part are compared with desired dimensions and the core box and pattern are modified where required. They are subsequently used to make production cores and molds formed from same sands under same conditions previously employed. The production cores and molds are accurately assembled and gauged and production parts cast at the same temperature previously used and are cooled as before.