[Retlaw]

Originally Posted by rtbarton

That's interesting, patterns are usually made oversize to allow for contraction when the metal freezes. I would have thought that using a part as a pattern would produce too small a casting.

Thats why I included the term give it a good rapping, a metal spike is inserted in the origanal casting, and before it is removed from the mould, it is rapped well, this causes enough movement to make up for some of the contraction losses, 1/120, whch is roughly 3/32nd of a inch per foot.
Retlaw.