The double roller is interesting and clearly beneficial. The efficiency of an apple mill is predicated on roughly three factors:Double crushing like this would help factor 2 a lot. I suspect that you could have left one of the lower rollers as an idler roller and had it work almost as well (this is common on grain roller mills, might be more problematic here due to the slipperiness of the apples). A floating scraper to peel the pulp off would probably help that (and wouldn't be a bad idea anyway)...
- the power of the press (the more more powerful it is the less important the rest are)
- the fineness of the grind
- the rate of the pressing (slower is better otherwise the apples "cake" up and won't release the juice if you go to fast - kinda like case hardened wood).
I also like the teeth, I've used screws (heads exposed) and old crosscut saw teeth for similar (the saw was toast so no loss, don't yell at me on this one guys - cut a kerf, cut the saw off just below the teeth and pressed into place, I think it might have been pinned in place as well but its been a long time), these look a lot better although I don't think they would get it fine enough alone (hence the second roller).
If you were doing a lot, I'd want the crusher on a platform so you didn't have to bend over to pickup the crushed apples.
Once again a nice build with a lot of subtle tricks if you look close enough
Thanks for posting!