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Earthman
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The rule of thumb in the my old machine tool tech textbook is that casting patterns should add an extra 0.125" on precision mating surfaces. Then machined to tolerances with a secondary operation like thread cutting and facing. Metal casting like injection molding uses a sprue and gate system for mold flow but can accommodate a much greater variation in wall thickness. Ceramic shell investment process requires no draft angles as the part is broken out of the ceramic as a one-off waste mold.
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ralphzoontjens
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Thanks! That must be 0.0125" extra instead of 0.125" I assume. If threads always have to be machined after casting this is going to be a bit above budget. I hear some factories can work with close tolerances up to about +/-0.010 in/in.
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