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Another Cincinnati #2 Tool & Cutter Grinder question - Lower Pulley


Jul 17, 2005
Annapolis, Maryland
I'm working on my grinders "drive system", and have a question about the lower pulley on the motor. OK, several questions ...

Does anyone know if the nut is left, or right hand?

My grinder, which was in really good shape when I got it (because the last owner rebuilt all of it), has a plastic pulley on the motor shaft. I had thought the last owner had made a new pulley out of plastic, but when I looked closer, it is not a home made pulley. It is an injection molded part. The back side by the motor is "hollow" with ribs. Did the late models switched to plastic? The small diameter step is heavily worn. So much so that the belt does not track. The last owner put shims in the adjustment mechanism to keep the belt from riding up on the large pulley (which binds up everything and stops the motor). If I remove the shims and run on the large pulley, it tracks properly. So I'm going to replace the pulley.

I was going to make a new one from cast iron, but I'm wondering now that the plastic one looks like it may have been original. Though if it wears that badly, I still may go back to cast iron. The friction coefficient has to be better with cast iron.

Does anyone have a spare pulley?

Or insights into why the pulley is plastic?

And most importantly, which way does the nut rotate?

Before posting, I back calculated the spindle speeds. The pulley can not be original because it does not have the speeds listed in the Cincinnati manual. And since 80% of the wheels that came with the machine were 7", they guy probably did it intentional. The pulley has 2.72" and 4.19" pulley steps, which gives 2660 and 4100 rpm. Looks like the pulley should be just under 4 and 6".

There is a picture someone posted here of a motor pulley -

The size in this picture looks like my current plastic pulley size, and not like 4" and 6" diameter. Thoughts?