I have to confess that I don't know the metric conversion but if the leather is too thin you will have a problem. Some folks will shorten the post or add a small leather 'washer' to the post side. There are several other posts that can provide more details if search.
saw an old industrial for sale on craigslist. I am not interested in the machine but was curious about what appears to be a speed reducer but was not sure since the pulleys don't seem to be the right size. Anyone know about the piece on the right?
I had a similar problem from a servo motor. Thankfully it was under warrant and I got some of my money back but I got a lot of grief from the seller, one of the sponsors here... is yours under warrant still?