This is a hand-cranked spool winder that I 3D printed in the background while doing other things. It's not my design: I used this one.
Printing the gears (July 2023)
By July 13, 2023, the printer had gotten to the gears. They're herringbone gears, along with a worm and a shaft.
Assembled (July 2023)
A week later I had it put together and winding a spool.
Here it is in action.
It works pretty well, but it was kind of a pain to assemble. Lots of the pieces didn't fit without sanding, and I bent or broke one or two of them trying to get them together. Still, I'm pretty happy with the result. The gears are pretty good. The worm gear kind of sucks, but it works nonetheless.