F.A.S.T

This was almost exactly what I was looking for, and would help me out tremendously if there was one more sliding bar: expansion ratio. By having a sliding bar that lets you choose how much the spiral expands (like a nautilus shell), you can alter the curve of the spiral to best please your own eye. I suppose it stops being an Archimedean spiral at that point, but it would be great for the craftsman to have the option.