[dmforcier]

That's a good point. On the router the movement per crank was pretty small, but they were going for precision. I think it 1/32" per turn. But one doesn't have to use a fine pitch thread. You might be able to go something like 4:1 (4 turns per inch). With a mechanical advantage on the worm, that wouldn't be hard to turn.

The router table was direct drive (crank on one sprocket) with a bike chain to the other sprocket, but as I say, a fine pitch.