ATM Advice re: tube rings

[kbarger@haverford.edu (Kyle Barger)]

I'm having trouble cutting tube rings.  The actual cutting of the circles
is fine (thanks to all the wonderful advice in the archives), but I can't
get the right size.  My tube is 6.5" OD while my router's base is 6" in
diameter.  I have so far succeeded in cutting rings with inside diameters
that are too small, or too large, but the base interferes with placing a
nail to pivot at a 3.25" radius.

So, can anybody a) tell me how to make the correct size cut or b) give
advice about completing the scope without the use of rings on the ends of
the tube.

--
Kyle Barger                          Haverford College
kbarger@haverford.edu                Academic Computing