I haven't tried it, though given everything else I've milled in my coffee
grinders, I think it would work. I think your biggest issue would be
volume - you might wind up burning out your coffee grinder. When I was a
kid my parents had a wheat grinder and the sound it made was ear-splitting
- I haven't looked at them in 20 years, so I would think they would have
gotten quieter, but that noise would be a deciding purchase factor for me.
In short, I think your coffee grinder is worth a shot - and not to
expensive to replace if you burn it out. (I'm thinking of little home
kitchen coffee mills.)