Dave Hinz wrote:
I'd like to sort a large quantity of disks by weight. They're 0.75" in
diameter and the two type have a mass of either 3.1 grams, or 2.5 grams.
Little to no deviation of those two values from sample to sample. I can
think of a couple ways to do this in an automated fashion, but I'm
interested to know how a problem like this has been solved previously.

Alternately, the disks in question have a different density - SG of one
is around 9.0, SG of the other is around 7.0 - is there a reasonable
substance with a SG of 8-ish, that I could use to differentiate them by
which ones float? I'm thinking not, but...

Molten zinc or tin? Or molten iron, but it'll probably destroy your
discs. I can only think of molten metals which have a density that high.

Are these coins by any chance? If so, it might be worth looking at how
vending machines work. Some have rather novel ways of sorting coins.

Chris