Step 5: Ring Cutting Jig
Start with a 22" by 11" piece of 3/4" MDF. First, mount a stop on the underside of the board five inches from the trailing (short) edge. The stop will need to clear your bandsaw front fence rail and stop the jig-board at the front of the bandsaw table. I used several nails for the stop, cut very short in order to clear the front fence rail. You may use a wooden stop block, or whatever fits your bandsaw. The jig will slide on your bandsaw table along the fence and into the blade.
Once you have the stop installed on your jig board, set the bandsaw fence for 1-1/2" and run the jig (stop down) along the fence into the blade until you hit the stop. This will cut a straight line (kerf) into your jig 1-1/2" from the left edge. Back out from the bandsaw. With a carpenter's square, draw a perpendicular line from the fence-edge of the board to the end of the cut and extend across the board. This line represents the front edge of your saw blade. It will also be the line on which you will locate the pivot points for cutting the circles for the bowl.
Drill a 3/32" hole on this line 3-1/2" from the kerf (i.e. 5" from fence-edge) and insert a 6d nail. This pivot point will produce a 3-1/2" radius, i.e. 7" diameter circle (Fence still at 1-1/2" as before!).