Hy C10 - C90 Bill, my experience is more with truck/bus drums, but I have seen them typically .010" -.020" undersize when new, I believe this was done so we could cut any mounting distortion out of of the drum, and still be at size or slightly under size. This may be the case with smaller drums as well, hope that helps.
3B, I was hoping that you would drop by.
Edit: I just re-read what you wrote and now see that if I made it at 11 inches, and it is under sized, it will not fit. I'm wondering how the Professional Made Micrometers are set?
Maybe I could set up the Indicator to show both ways? Undersized or Over.
Bill
