Can you turn it around several turns all the way around without any grittiness? The clearance between the moving rotor and the stationary rotor is quite small. Mine's gettin' pretty old, so if it doesn't get turned on for a week or so, it rusts itself locked. It's a cheap galvanized Badger. I was ready to get it replaced, so I said what the heck, threw a few cherry sized rocks in there and ran it for ten seconds or so and haven't had a problem with it since.
It's a 1/4" hex on resi machines, but apparently there's a different tool to dejam commercial units.
There might be a coin or a metal crimp ring used on ends of tubes of ground meat. or a string wrapped around on the shaft.