Found a stat about sand grain size that blew my mind

Was reading a metalcasting handbook from 1978 I found at a flea market. It said the average green sand mold has like 60,000 grains per square inch. Never thought about it before. Has anyone else looked into how grain size affects surface finish on ductile iron?

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ninal914mo ago

The AFS (American Foundry Society) did a study back in the 80s on this specifically for ductile iron. They found that grain size around 140-160 AFS fineness gave the best surface finish without causing too much gas related defects. I remember reading that finer grains like 200+ actually made the surface worse because the sand couldn't vent properly, trapping gas and causing pinholes. Coarser stuff like 80-100 left a rough, grainy surface that needed extra grinding. It's wild how much the grain distribution matters too, not just the average size. If you get a tight distribution with mostly similar grains, you get way more consistent results than a wide mix.

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wren_rodriguez4mo ago

Chris from Waupaca told me the AFS 85 study had a follow-up in '92 that nobody talks about.

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