Recently had to use the rotary table on the milling machine but did not have enough headroom to center it with the co-axial indicator. My milling table is mounted on a circular column so there is no possibility to lower it down, indicate and putting it up again without loosing the centering. Came up with the idea to use a 30mm range dial indicator. Unscrewed the tip and made a quick perpendicular extension enough for clearance. Worked beautifully. Can indicate holes ranging from around 50mm to 110mm diameter.