I took a class in stone setting and this is what I learned:
- Assuming that the prong tips are level use a cup bur on all
prong tips using a circular motion. This will put a cut in the
inside of the prong tip(and a little on the outside too, which
when finishing you can file it down.) The cup bur will round off
the prong tips and put a mark for notching.
2.Use a 45 degree heart bur to cut a notch on all the prongs.
Keep on checking with a loupe to make sure that they are all
level. Cut the notches with the heart burt until 50% is cut.
3.Using the tip of the heart bur cut away below the notches to
deepen pavillion angles.
Anyway, the above is what helped the most in cutting notches
accurately. I took the class from Colonial workshop. If you
need the person's name and phone number let me know.