Many large castings, the patterns of which would require a great amount of material and labor, may be molded in cores. In this process no pattern is used, the practice being to make a core-box of some part of the casting and, after baking, to assemble the various parts in a flask. In many cases this is not the most economical method, but it is sometimes used of necessity because the peculiar shape of the required casting makes it impossible to draw the pattern if it be made in the same shape as the required casting.

As few castings are obtained without the use of cores, it is essential that the pattern-maker give this branch of molding close study. The proper location of core prints on the pattern may make the difference between success and failure.

Any pattern could be so designed that it might be molded in cores, but such designing is economical only where a duplication of parts formed from one core-box is possible.