So I learned a thing today...well several things. Rotary tables

[Sticks]

And now I have learned a few more things.

 

[homebrewed]

My smaller RT also has a straight hole, no taper. It has 4 T slots sized for 8mm T nuts, which are used to mount a 3-jaw chuck that came with the RT. To center the chuck/RT I chuck up a small dowel pin and mount a DTI on the spindle. Basically a simple (cheaper) version of a coaxial centering tool. The procedure from there is similar to what you'd do with a centering tool.

 

[ChazzC]

My smaller RT also has a straight hole, no taper. It has 4 T slots sized for 8mm T nuts, which are used to mount a 3-jaw chuck that came with the RT. To center the chuck/RT I chuck up a small dowel pin and mount a DTI on the spindle. Basically a simple (cheaper) version of a coaxial centering tool. The procedure from there is similar to what you'd do with a centering tool.

I have a Sherline RT that is the perfect for my Mini-Mill. It has a threaded center hole with a 7/16” locating hole. Sherline’s 3” self-centering chuck screws onto an adapter that locates on the hole so I use a 7/16” precision ground pin to center the RT and then mount the chuck.