The angle of the cut depends a lot on the thickness of the wood and what depth you want to cut and the blade you are using. It is somewhat like cutting the rings for a bowl or vase. About the only way to find the exact angle is to do a few practice cuts on scrap. Once you have found the angle that works for you, write it down and be sure to include the thickness of the wood (3/4"). the blade used (FD #5) and maybe even the type of wood (oak) for future use.
Some times if I want a large, shallow bowl out of 3/4" cherry, I use as much as 45 degrees and a much wider spacing between cuts. On the other hand, if I want a tall vase out of 3/4" cherry, I use a much shallower angle like 20 degrees and can use narrower spacing between cuts.
This project, the spiral cutting, takes more guessing (especially doing it freehand) so I suggest a practice cut or two using the same thickness of wood and getting used to keeping the same distance between cuts as you go.
What this all boils down to is........ IT AIN'T AS EASY AS IT LOOKS!
Rog
