A method of casting metal in a gas permeable shell mold in which a vacuum is applied to an external upper mold surface by engaging the mold in the downwardly facing opening of a generally cylindrical vacuum chamber, defined by a chamber wall with a threaded region sized and shaped to snuggly engage a side mold surface. Engagement is effected by forcing the mold into the chamber opening while causing relative rotation of the mold and chamber.
展开▼
