Lessons Learned Putting a Flat Edge on These Rings

This is the setup I am using to put a flat bottom on the rings to simplify screwing them to a flat base.

I have a spacer between ring and chuck and I would still have preferred a bit more space between mill and chuck.  Next time, I will start with a 1" thick ring, cut the flat spot, then back to the lathe to remove the half inch closest to the chuck.

Maybe simpler would be to put the ring in the vise and slice off a chord then use the setup above to drill the adjustment screw holes.  I will do that for the other ring.

I chewed up that ring cosmetically and put the adjustment screw holes at the wrong positions.  There are 180 degrees in a triangle and they form a triangle, right?  But they are around a circle so that should be 120 degrees apart.  The extra holes will not be visible and slicing 1" slices of 3 1/8" stock on the chop saw is harder the shorter it gets.

More lessons: cutting a chord is harder than it looks.  Acetal is not Teflon, but it is very slippery and hard to hold securely in a mill vise as the mill cuts across even at  .1 inches/minute.  So I am cutting across the edge.  This is multiple steps and I see no reason to write code for a rare operation. 

I may have just tried too deep a cut.  .05" seems to work.