This is where I had thought about mounting one of my Barker mill columns on my big lathe’s (22“ ) saddle.Proving once again that, no matter how big your machine, a job will always come in that's too big for it.
A method I have used many times to radially index a part where high precision is not needed. Use a strip approx 2" wide of heavy paper or thin sheetmetal (Aluminum flashing works well) and wrap it tight around the pipe, scribe where the end overlaps and cut there. You now have a strip the circumference of the pipe, you can lay it out flat and easily measure your divisions. wrap it back around the pipe and you have your index points. You may not even have to transfer the marks to the pipe, if you can rig some sort of pointer affixed to the machine. Of course you can reuse the strip for multiple parts. As I said, it's not for super precision, but you can do much better than 1/32" if you are careful.The channel concept reads the most clear and straight forward approach. Thank you. Yeah, I may have to use a tape along the OD to scribe and index manually. Tolerance can be up to +/- 1/32, give or take. I thought of methods to use my 10" rotary, but the size of work is formidable.