recommendations for a heavy-duty grinder for roots

we've harvested a healthy batch of nettle & knotweed root and are now trying to process. the herb grinder we have just ain't cuttin it, both in terms of size and grinding ability. looking to upgrade, but all i've found so far is those commercial coffee grinders which start at about $1,000 and go up from there.

was wondering if anyone had any suggestions for a mid-range grinder that could handle roots/rhizomes without frying the motor and/or my patience.

any tips would be much appreciated.

I've been reading The Organic Medicinal Herb Farmer while planning my own medicinal herb business, and they use a small wood chipper to chop their roots. Way less expensive than a hammermill, but you can't powder roots with it. Still, I think for my purposes it'll work...

thanks, Jessica, that's a totally leftfield idea, i like it. unfortunately, i was gifted a heavy duty chipper that wouldn't process the rhizomes very efficiently, but does make darn good chips, so that idea's out for me.

funny, my better half also got that book, but i haven't cracked it yet.
medicinals are where it's at, yea?
bet you got some good chaga up there in Maine.
i was listening to a talk about lyme & herbs and they were discussing rhodiola as one of the remedies.
you might have a good climate to grow that...