Originally Posted by Astonlee  I found sometimes it's not the collet that the problem, often as not by just rotating holder by 180 degrees you cure it... |
So you are using runout in the taper to compensate for runout in the collet. Nothing is perfect, all collets will have some error, all spindle tapers will have some error; this is a case of two wrongs being used, maybe not to make a right, but at least, to make things less wronger.
Dead simple to do on a Haas, the holders go in either way.