Checking Perpendicularity Between Face and Centerline of a Shaft
Turn the shaft several revolutions on the blue V-block while keeping a continuous contact between the shaft face and the brown pin (for example by setting the base inclined).
Get max and min values (E1 and E2) shown by the indicator.
Non-perpendicularity P = (E1-E2)/2A
A: center distance of indicator and the brown pin.