Re: Where to purchase and learn to use a lathe TEST BAR?
Maybe I'm just cheap. A test bar only needs a ring on each end that's the same diameter and perfectly centered. Center drill both ends of a bar. Using a dead center in the tailstock, turn a clean area next to the tailstock. Flip the bar and do it again. Do a final pass on each end (flipping the bar and working at the dead center) using a shear tool (for good finish on steel), and without moving the crossfeed. You should have identical diameters on both ends, perfectly centered because it was running on a dead center.
Ideally it should be a tube to reduce sag. Maybe an iron pipe with a Loctited pipe cap on each end- turn the rings on the flange of the pipe cap.
I rarely have my Logan better than .0002"/" because my garage floor warps with the seasons and water table, plus it's hard to fiddle the tailstock much better than that.
BTW, once you have your lathe running with near zero taper, it's a good time to turn a cylinder between centers, then face the end at the same time (relieve the center area first). This makes a cylindrical square for your surface plate that's inherently very good. The commercial ones are excessively expensive. Heck, make two and you can compare them side to side just to be sure!
