Some time ago, I made a simple wooden shepherd's sundial. It's crude and doesn't work well, but I set it on a lanyard and occasionally use it. When I decided to use it recently, my wife asked for a small one as a necklace. Commissioned artwork time!
Since I wanted the sundial to be stylish as well as functional, I thought a bit about materials. I ended up with a simple design that uses 3/8" copper tubing. It's the same stuff that you can get at the hardware store for various plumbing jobs, but it's small enough for the task. I traced out the hour lines using a short python script, and printed them out for use as a guide.
The gnomon is held in a steel cylinder with a slight lip to retain it inside the copper tubing, which has a matching (reverse) lip bored in the end. You slide the cylinder in from the bottom of the sundial. Boring the copper was a bit of a problem until I got the boring bit set properly. I also ended up bursting through the side of the first cylinder because I didn't correctly account for the thickness of the tubing.
I cut the tubing with a jeweler's saw and filed it to final shape for the noon curve. The cylinder has two drillings: an axial drilling for the hanging loop and a radial drilling for the gnomon. The hanging loop is just a piece of brass wire bent into a loop at the top. I thought of soldering it in place, but decided not to. I hammered the bottom end of the wire into a small rivet, so the loop is free to turn.
Here is a trial assembly.
I spent considerable time polishing the copper, the pin, and the cylinder. The machining was not too arduous, though it did take a few tries, but the engraving was much more tricky.
Here's the final product.
I did not use a watchmaker's square graver (too unwieldy on the round surface) nor the more usual round graver (difficult to get it to bite consistently) to do the engraving. After a bit of trial on a scrap piece of copper tubing, I found that a very small screwdriver that I had previously sharpened to a narrow cutting blade worked much better for engraving.
To keep everything aligned, I taped the printout to the surface of the copper, and cut through the paper. This got the copper marked in roughly the right places. Then I removed the paper and finished the engraving under the microscope. This took about an hour, and was a bit nerve-wracking because every slip-up is visible. I'm not too proud of how the engraving came out -- many slips, wiggles, and other awful mishaps are visible if you look closely. However, it doesn't look embarrassingly bad if you don't use a microscope.
