Mills Castings

[thepennyarcade]

Hello All
Does anyone know if, back in the day, when Mills casting came out of the foundry sands were they smooth?
If they were rough to the feel, how did they sand/grind/polish them so they came out with a polished mirror finish?
I know a lot of the castings were painted but I suspect the aluminum was pretty smooth.
Thanks for your knowledge
Best
John

[mechanic]

Mills castings were made using investment type castings, these were very smooth ceramic molds and were reusable so many castings could be made using one mold. Rough castings are generally made for sand cast molds and can only be used once. Many repro castings use the sand casting molds, this is due to the high cost of making investment casting molds. So beware of rough castings as they may be repros!!!