Lathe roller centering tool

[rendoman]

Both work in the same way, no matter where the shaft is locked, the outer race of the bearing has to touch the not centered object. The guy in the video made the tool on axis with lathe spindle, my tool is perpendicular. About the bar, I had no square steel scraps available, Hex was pretty good for the purpose, a very strong shaft and easy to machine. Same for the bearing, a good one is ok.