I've used my bandsaw to make the initial cut then widened them with sandpaper. I fold the sandpaper over once and when that gets loose. I fold it again, and again til it gets right.
When I make reenforced self nocks I use a single cut with the bandsaw, a little from each side to be sure its centered, and a piece of rawhide for the spline. The rawhide idea came from Glenn St Charles's book, "billets to Bows".
I was worried about the rawhide as I was sitting in a rainstorm but they came through without a hitch. Pat