I think the OP did OK with his wording.
He got very good results with 3 pages of helpful replies and one negative sarcastic reply. So what if he couldn't think of the proper name for the thingy. Don't we all have moments like that?
That's exactly what happened. As it turns out, looks like the proper name for grinding thingys mounted on smallish arbors is "Mounted Points" Don't believe me, do an Ebay search.
I would like to thank everyone who responded with helpful ideas. I am in my late 60's, with limited verbal and mental skills. Also, I have no power tools except for a DeWalt Hand Drill. So I'm limited on the high precision side of things. I am trying to re-live my childhood motorbiking days and do it on a shoestring.
All I needed to do was remove somewhere between .005 and .010" from the ID of the sprocket hole. My tool of personal preference was a rotary grinding stone. If I had a drill press or a mill, I would have used a cutter. But I don't, so I didn't.
As it turned out, I was able to fit the sprocket to the wheel hub with a decent amount of precision. So I accomplished my mission.
Thanks again to all who offered helpful comments and emotional support.