When someone brings in a shaft to be reduced in size or retapered less than .25mm I will sand to that size. However, I will never sand a 1/4 mm or more. I put in new centers in the shaft and then turn down to about 1/10 to 1/20 mm over size and then just sand from there. I have found that when a shaft is turning fast enough to sand it no longer will run true but centrifugal force makes it whip some. When sanding, where the shaft is whipping, one side will sand more than the other side leaving the shaft not rolling true. It will look like it's warped although it's actually not, it's just that one side is sanded more than the other. This scenario will allow the tip to run true with the cue but in the center of the shaft, when looking for light, you will see a roll.
Dick
I've also found this to be true when sanding on a lathe but the round pole sander, a centerless sander, does a beautiful job when used with the proper belts. It also takes all the sawdust away using 2 dust collectors, one internal feeding a main unit. The wide belts and the adjustable feed makes it a great asset to a cue shop, but like anything else, if used improperly you could end up with toothpicks.