wrote in message
...
I was trying to make two rings from copper pipes, 1.625" OD (wall
thickness 0.061") and 2.125" OD (wall thickness 0.035")
respectively.
The length of the ring was to be 0.75".
...
However, when I checked the final product with a square it was
obvious
that neither plane of the ring was square to the sides. I did an
additional check with a height gauge with the ring on a flat (well,
as
flat as I could get) surface. There was a difference of 0.017" in
height of the ring around the circumference.

Michael Koblic,
Campbell River, BC

I can't make good rings that way either. I'd turn a wooden mandrel and
slide the pipe onto it, then part off the rings.

You can turn a shallow parting groove and use it to guide the bandsaw
blade. Saw a shallow cut, then rotate the work a little in the blade
travel direction so the flexible incoming blade rubs on and is guided
by the wall of the turned groove. Saw in a little and advance again.
Unless the blade is new and sharp it won't dig into the wall of the
groove much. Once the saw cut extends all around the blade should cut
the piece off squarely, or if not you can see it deflect.

The same trick can cut under the hard shell of a scrap hydraulic
cylinder rod with a tool you can easily sharpen rather than the
expensive sawblade.
jsw