ATM trepanning diagonal

["Jerry B. Hillman" <JBHillman@ev1.net>]

Hi all,
I finally got my diagonal blank figured the way I want it.  Straight fringe
lines. Now I need to cut it and then I suppose I need to recheck the figure
and touch it up if cutting it relieves stress.
So far the only tubing I have found that is big enough is exhaust pipe. This
needs to be between 3" and 3.25". 3.125 would be ideal.  I attempted to form
a cutter from flat 24 gage steel but was unable to make it round on the free
end.
If anyone has done this and has some suggestions I would be happy to listen.
I only have two blanks and I want to end up with one useable diagonal. (my
third blank is too short.)
Clear skies, Jerry