Check on Ebay, look for Federal TestMaster T-1, they are what I've been using for 30 years, they're out of production, so there's no new price and the used prices are not high. I just used one to center on a piece .125 OD, on my mill. I built a clamp that mounts on the spindle, and holds the indicator. It (the indicator) can be adjusted to read either ID or OD.