I use the RT to cut hex , square, 7 sided polygons, etc. It can be done with the RT set either horizontally or vertically. I use the RT horizontally for short work and side mill. For longer work, I set the RT vertically and end mill. My RT has a 1.000 center hole and I made an adapter so that I can use either my three jaw chuck or my four jaw chuck. I have a threaded plug and a drawbar to secure the chuck. The chuck for my 4th axis RT for the Tormach has a backing plate with a flange for clamping via the table slots.
To cut the polygon in the horizontal mode. I have my 4" three jaw chuck mounted at the center of the RT. I will mount my stock and set the table so it is off side on the x axis and make a trial cut by moving in the y direction. Rotate the table 180º and make a second pass in the y direction. Measure the distance between the two cuts and adjust the x axis appropriately to reach the final size. Rotate the table by 360º/ no. of faces after each cut. This works well for even sided polygons. For odd sided polygons, where it would be difficult to measure the size, I would make two skim cuts 180º apart and measure across the flats. The x axis center will be 1/2 the measurement.
If the cylinder is already to dimension, the work has to be centered to the RT axis. To that end, a four jaw chuck would be a better choice. I would center the work much like on a lathe by rotating the RT. When the work is concentric with the RT axis, I can proceed as above.
Using the RT in a vertical configuration is done in a similar manner except you are using the end of the cutter.