Re: Model R.R. content- brass casting

As Bill mentions above, you get shrinkage between the object that makes the cavity and the finished object, so using someone's already produced properly scaled product as a pattern will give you an undersized replica. If you use the investment casting process ("lost wax"), you will have shrinkage between the original pattern and the wax patterns, and another shrinkage between the wax patterns and the finished product. The shrinkage percentages will not necessarily be the same as the materials and temperatures are different.

Considering the amount of time and money you will have invested by the time you can actually produce castings, you should make you own properly sized patterns rather than trying to use someone else's product as a pattern which will not give you accurately sized castings. It's OK to use the existing casting as a model but you will have to enlarge all its dimensions to get good results.