If you're lucky, which I was, the camera had an empty 620 spool in it. You can put this on the receiving side, to let the camera reel the exposed film onto. So the challenge is just to get a roll of fresh 120 film to fit onto the unexposed side.
- I tried shaving the ends down to a narrower diameter with a Dremel. This was really ugly.
- Clipping the ends down with large nail clippers worked pretty well. I recommend it.
- But my favorite was using a pair of electricians' scissors to trim down the diameter. Clean and easy!
- Some folks recommend thinning it down with a metal file. I'll bet that works nicely.
- I tried using the Dremel with a sanding disc, and it was a little sloppy. (But worked.)
- Better was to use the cylindrical sander attachment for the Dremel. Nice and tidy!
So now I've got an empty 120 spindle that fits in a camera that takes 620 film. I'll try pulling 120 film off another spindle and feeding it back onto my make-believe 620 spindle. Then I'll try taking a loaded 120 roll and trimming off the ends with the unexposed film still on. And after that, well, you can actually still buy 620 rolls, it's just a specialty item.
I'll report back with details about what worked and what didn't.