My model 17 suddenly started to have metal on metal grinding. I can turn the unit from the top and from the bottom with the wrench and it does spin when engaged. Any advice out there? It was working fine 5 minutes earlier... thanks!

Are you sure you didn't drop anything in it?. I just had a customer of mine drop 2 pennies in theirs. The hammers could have worn out the mounting rivet or the bearing may be bad.