M42 mount to M39 lens adapter (for enlarger lenses)

I wanted an adapter to test some enlarger lenses, and found dunga's adapter. The only issue I had was that the M39 threads were too large - the lens fell into the recess without grabbing the threads. However the M42 threads were perfect for a cheap EOS EF to M42 adapter ring. I cut the bottom off, shrank it to 98%, re-joined and off we went - fits perfectly for my enlarger lenses. I also flipped it upside down so that no supports are required. dunga did the hard work grabbing the bits, I just tweaked it a touch. I printed at 100mm/s, and ended up with a print time under 30 minutes. Additionally, this will take under 1.5m of filament. As recommended, use black filament for camera use (not in a darkroom). No, this does NOT focus the lens, but that wasn't the point for my experiments (to determine UV transmission of the lenses I have).