Here’s the charcoal grinder that I built.
You don’t even need bearings, could just drill holes in wood to fit the shaft. I eventually made a hopper for it and I set the grinder on a table that is over a plastic child size pool, a tarp or anything else would work I just used what I had.
Take round bar and flat bar, drill holes in the flat bar and braze or weld into teeth.
Then opposite of that make the static teeth with about a 3/8" gap.
With a 17" steering wheel I have enough leverage to bend nails.