EDIT: I updated the DXF file to now include a self-storing pocket for the small gear. Finish off the gear profiles (both small and large) with a 1/16" [1.5mm] cutter.
This could be a fun little project to make for the kids or grandkids. Some time ago I ran across a Spirograph geometry set and finally decided to give it a cut. Didn’t work very well, gears kept jumping teeth. In fairness, this may have been the fault of the PVC material which is not very slippery, therefore not a great choice. But I just didn’t care for the geometry of the teeth. That sent me down a rabbit hole in search of another option, where I came up with this little beauty. It was on a 3D printing website, so I had to take the STL file and convert it to a DXF file. From there, I reverse engineered the gear teeth to 2D perfection.
However, the one with the DXF file provided here works great! This one is unique because it has a lip that keeps the gear in place (keeps it from lifting up) when using. Use whatever materials you want. I used 1/8" PVC on the larger part and HDPE on the small gear. PVC is not great for this application, but it’s what I had onhand & just wanted to test out the geometry. I cut the pocket depth .070" to clear the 1/16" HDPE material.
SPIROGRAPH.dxf (60.8 KB)
Don’t waste your time with this one if you happen to run across the files for it (the one pictured below).
Here’s the web page for the one I provided the DXF file for. I didn’t look, but you may find additional small gears for it.