I can't forge to a couple thousands tolerance either, but i can get close enough to make a working slip joint finishing with files and sandpaper. My biggest problem is keeping (or making ) everything flat enough to look good, it really doesn't take as close a fit to work (and work well) as it does to look professional. I think a belt grinder with a good platen would help alot over files and sandpaper. And if I was looking to sell folders I would certainly try that as for now this is a hobby (when I made my first one nobody told me I couldn't do it hot with a hammer so I did
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