Tramming a mill with a coaxial indicator
Update: Another youtuber has another option for this operation that uses the base of a swivel vise which I like very much. See • Video
Update: This video seems to make people crazy so I'm working on a longer update that shows that yes, using a coaxial indicator is a very good and accurate way to tram your mill and that in this mode, the probe length does not matter. Why? Because we're measuring angle, not x, y, or z dimensions.
Use a brake rotor and coaxial indicator to check the tram of your machine. Added a short section showing how to center a bore under the quill.
In the second half I'm adjusting the Y axis to create then remove needle deflection for that axis. The objective is to reduce needle deflection to zero in the X and Y directions.