Creating the Jacks game pieces in the last project, refreshed a memory for many years ago of a similar creation with only four arms instead of the more usual six arms. The problem is that I could not figure out how to turn a four arm piece without a lot of carving. After all, I prefer woodturning to carving.
The problem here is the lack of opposing points on which to mount the wood. The six arm style is easy since everything is at 90 degrees. A four arm style implies 120 degrees. However, in practice the 30 degree difference is significant. I spend some “quality” time with Google AI settling into how to layout a tetrahedron on a sphere. A tetrahedron is the base platonic shape for the four arm jacks piece. While a 6 arm style could be laid out on a cube, creating a tetrahedron is a puzzle by itself.
In the end of the series of questions and responses, the solution boiled down to:
- Marking longitude lines at 60 degree intervals;
- Marking intersections on the longitude lines at a specified distance from the equator. Google was happy to do all the calculations for me.
After all that, turning could proceed:
- Turn a sphere, mark the equator, and measure the diameter.
- Ask Google for the distance of a tetrahedron vertex from the implied equator given the diameter.
- Mark intersections alternating north and south from the equator every other longitude line.
- Cut temporary dovetail tenons at all intersections and the north/south poles.
- Drill to insert dowels to reinforce short grain in all arms.
- Successively, mount and cut away wood as much as possible or dared.
- Repeat until the center become apparent and acceptable.
- Mount to a collet chuck or padded narrow jaws on the four arms that are to be preserved. Cut away the opposing sacrificial arms.
Done!
That’s all – Right. Well, start with the six arm version until you can visualize this one.
This wood is poplar, the Jacks piece is about 5 inches diameter, finished with walnut oil.
I love it.
Enjoy.
p.s. Would you like a more in depth demonstration? Please contact me for an IRD (Zoom Demo) on this or other topics.
If you happen to have technical difficulties, this video is also posted on YouTube. But it is best right here. So stick around.
