I don't have a 4th axis yet but have always been curious how to setup a 4th axis on a knee mill accurately. Is it as simple as chucking in an accurate round bar and using a dial indicator as you would setup a vice? TIA

Yes! Indicate the body of the rotary table just like a vise, and then indicate a gauge pin or similar. Using a known diameter pin lets you find out the exact centerline-to-table distance, which is useful for setting toolheights to the 4th axis centerline.

Thanks.