I built another electromagnetism demonstration device for the Spark Museum. I wanted to make one where the needle was actually moved by electromagnetic action, not mechanically as the previous version was done. Pretty much everything was made on the Glowforge.
The 16" compass face was cut from Home Depot white/blackboard (whiteboard on one side, blackboard on the other). This stuff engraves amazingly well, with pure black engraved areas. The legs were made from Plywood that I had finished previously. The coil form and surrounding box for the Schweigger Multiplier were cut from acrylic. The heart of the thing is a little piece that I cut out of acetal, that holds a neodymium rare -earth magnet. I had to have a tapped hole for the meter shaft that went perfectly through the center of the two tabs. After a few failed attempts to get it centered I had the idea to cut a rectangle around the holder and use that as a reference to drill & tap the hole. It worked great. Here are some photos:
Edit: Here is a short video of it operating.