Quick Reference: Finding Machine Rotary Zero PositionFor Table/Table Machines:

Step 1: Level the A-axis. Step 2: Find X,Y center.

Step 3: Rotate A+90 and set dial indicator to Zero.

From Secrets of 5-Axis Machining by Karlo Apro

Step 4: Rotate A-90. Dial indicator should read Zero

Step 5: Jog Z minus the radius of the rotary table diameter, and adjust gage tower height to match.

From Secrets of 5-Axis Machining by Karlo Apro