Argghh. I usually try to stay away form this stuff, but........If you are working on a wood lathe, that amount is nothing. Your diameters, parallelism, turnism, finishism (sorry, got carried away) is controlled by............You and the tool you are using. If turning with hand tools how far off the centers are is a moot point. Now, that said, if you are using anything that holds the mandrel 'rigid' at the head stock, like a mandrel saver, you may have some pull on the mandrel, but it will all be the same direction, which, if extreme, can cause issues with the mandrel or center bearings over time, but...... If you turn between centers, you may wear the centers of the bushings a bit. Wood lathes are designed to turn wood between a drive center and the tail center. What we do with pen turning is not beyond its capability, but to expect precision from a wood turning lathe is a bit much. I have never checked the alignment on either of the 2 jet lathes I have, EVER in over 15 years of pen turning, and I turn 90% of mine on a mandrel. As a machinist I am pretty darn annul about things, but this expectation is not one of them. Just my .02. Next on the soap box