to check for 90° I just use a good 12” metal ruler and clamp it on edge between two spacers on the spindle then measure with a dial micrometer at several places between it and the table as I rotate the spindle by hand. When checking run out on the spindle it doesn’t really matter if it’s 90° or not. You’re using a dial indicator stuck to the table with the tip against the spindle again rotating by hand.
Steve Jenkins, McKinney, TX. 469 742-9694
Always use the word "impossible" with extreme caution