Quote Originally Posted by Wildwilly View Post
The problem with using 2 DI is that you have to be ABSOLUTELY square with your post. Not so just using 1 DI & rotating it......as you have found out!
So all of your fancy milling was for naught!
Jeez, way to disregard someones work...

If the tool's frame its tilted (and thus the indicators) with respect to the post, it'll result in one indicator tip being lower than the other, and one tip will be closer to the center with respect to the other. The up/down discrepancy is irrelevant, as the indicators get zeroed on the same point of the table. The inward/outward tip offset does create an error of the measured head tilt, but it is plenty small, say two tenths if the head is out of tram something like 0.005" over 5 inches, with an indicator tip to spindle axis distance variation of a massive 0.1", and said error decreases as you get closer to perpendicular.

Besides, you can always do a final sweep looking at just one of the indicators to confirm everything is good if you so desire.