Rings and tubes are tricky, especially when they get big like this. I use a set of plate jaws for my Axminster chuck with custom wooden jaws, which I can shape to hold whatever awkward shape I need to. These are not too expensive either so worth a look, depending on your chuck.
Alternatively the cole jaws and similar versions would do it too for a bit more money.
Work what you can from a solid piece and get if to a sanded finish. Part off only once you have done all you can to about 3/4 of it. Remount it on your custom jaws and finish the last little bit.
You can do it on a jam chuck but this is tough if you are only starting out. I always think its ironic that jam chucks are a great way to turn so many things cheaply without a chuck, the trouble is it takes a lot of practice to get the skills to consistently use one!!
Sharp tools and good presentation are vital here, shear cutting is going to work well on this job.
Hope this helps
Richard
