On Sat, 19 Jul 2014 16:16:03 -0700, wrote:

On Fri, 18 Jul 2014 18:33:37 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

fired this volley in
m:

You have hit the core of the problem which is the deformation of a
thin-walled conduit while cutting. Following on from your thoughts I
suspect I should get much better results even using a hand cutter if I
put a mandrel through the conduit first. Maybe even a wooden one.

ALWAYS use a close-fitting mandrel when cutting thinwall _anything_.

'Rule of thumb'


Besides, do you want to then have to chamfer the i.d.? I use the
closest-fit I can get, and hard enough material so that the pipe cutter
won't cut into the mandrel. I can always re-sharpen the wheel, but
sometimes it's tough to get a short piece of tubing off a mandrel where
the tube has been swaged into the groove in the mandrel.


LOL!

I discovered this little fact probably as you were writing about it. I
grabbed the first piece of wood I could find which was a pick-axe
handle. I put the brass conduit as far as I could on the handle taper
which turned out to be too far. I cut a nice ring and now I have two
pieces of pretty brass decoration as neither piece will come off due
to the phenomenon you described.

I cut a second conduit lower down on the handle with a good result.

Michael Koblic,
Campbell River, BC
Greetings Michael,
The reason I suggested a slightly undersized mandrel is because the ID
of the tubing will shrink some. But the other important feature of the
setup I suggested is that it limits the deformation because only one
cutter is used. This is because the tubing is supported right at the
pressure point. If more than one cutting wheel is used the tubing will
not be supported at every pressure point and so will shrink.
Cheers,
Eric