Machining the inside of rings

I have had the Modelmaster mill set up for about a year now and I’m
loving it. The question I have is this, is there any way to machine
the inside of the ring. Obviously I would need a tiny very short
spindle or some other way to get a small cutter inside the ring.

I just subscribed to the list after pouring through the archives
endlessly amazed by everyones input in all sorts of different
subjects and I anxiously await any help you could offer.
Thank You

What is it you would like to machine on the inside of these rings?
David