From McMaster part number: 61005K51
It has a 3/8 bore on one side and a 1/4 inch bore on the other.
I would clamp the coupling to the 3/8 diameter drill rod and then chuck the drill rod in a lathe.
I would gradually open up the 1/4 inch hole until the Chiaphua gear just pressed inside the coupling.
Then I would tighten down the clamp on the 1/4 inch side and viola... ... you've got a nice 3/8 inch diameter shaft to work with.
By the way, I am NOT doing this, so I can only judge what I think I would like to do. Any other folks think this is a good idea or not?
Joe J.
P.S. I am assuming that you want to mate to the 9 tooth gear cut into the motor shaft and not one of the gears on the cluster. Did I assume correctly? JJ