Making Rings

I mentioned a few days ago a technique for turning down round stock too big for the inside jaws of the chuck, but that I had not tried it out.

The rings that I made starting with 2.75" black acetal rod turned out to be too thin for me to machine a flat spot at the bottom for screwing two machine screws into the bottom from the flat piece that connects rings and also attaches to the telescope dovetail. 

So I started with the 3.25" white acetal stock and managed to turn it down to 3.018" with that technique.   I wish that I knew where my center finder went.  With my coordination problems the center hole was less than perfect, but the workpiece were close enough to concentric to stay in place while I turned them down to the diameter that fit into the 3" chuck where I was able to use the boring bar to enlarge the 2.125" Forstner bit hole to 2.201". I was thrilled to have the OD and ID within a few thousandths of an inch of each other and with enough wall to cut a flat on the bottom.  I will use a rotating table for getting the adjustment screw holes 120 degrees apart and the flat evenly spaced between two of them.

I started with black acetal but my acetal scrap bin yielded blocks to let me do it all in white.

One ring was ever so slightly thicker than the other but because I want to get the holes exactly centered when I do that operations I worked them down to .005" difference.  That is good enough.