## Spiraling into control

I am building a table for my Handibot as one of my biggest challenges thus far is registering the machine in the same spot when I move it to change bits. The table will have dog holes bored every 3 inches. The Handibot will have a fence and work pieces will be clamped against the fence via offset clamps.

Rather than cut circles and mount them offset, I decide to make cams based on the Fibonacci spiral. I am not sure if there is any advantage or disadvantage to this. My reasoning was that a spiral would have a smoother transition in clamping. We’ll see how this works in practice.

I laid out a rectangle and spiral based on the Fibonacci numbers with a pair of dividers. Alternatives to using dividers/compass include:

- Multiplication – the 3″x3″ square is effectively the number 8 square in the picture below. To make the 5 square, multiply 3 by 5/8ths. The 5 square is 1.875″ x 1.875″. To make the 3 square multiply 3″ by 3/8ths and you will find the 3 square is 1.125″ x 1.125″
- Print a spiral. Adhere the paper to your work piece with spray adhesive and cut it out.

I laid out a 3″ x 3″ square on a scrap of 3/4″ thick plywood. I set my dividers to divide the square into 8ths.

From the outer corner of the 3″ x 3″ square I paced out five spaces. This is the corner for my 5 square.

I repeated this process to create the 3 square, 2 square, and 1 squares.

I used a compass with a pencil to trace the arc in each square. The compass legs are spaced the length of a side of a square.

Then I cut out a small rectangle from the 8 square. This provides a handle for me to grip when tightening the clamp.

Next I used my fret saw to cut the spiral. I used a sander to sand down to the line.

I drilled a 3/4″ diameter hole in the spiral for a dowel. The dowel is 1.5″ long and glued in place.

The clamp does hold pieces against a fence, but I am unsure if it will be strong enough while using a CNC router. I’ll report back with those results eventually.