I have a good original brake drum, but with a worn welded on sprocket. I want to turn the rim of the drum back down to match the shoulder inside a NOS sprocket, and also check the run-out of the braking surface. Do I use the bore inside the drum as a concentic reference using an arbor, or do need to think about the mounting holes and peg locations for my reference. The bore inside the drum appears tapered. I can't get anything in there to measure.
Thanks in advance.