Anyone who is interested in this sort of thing may wish to take a look at the seven-book Build Your Own Metal Working Shop From Scrap series by the late David Gingery. While intended as a guide for the hobbyist, the series could easily serve as a blueprint for how to go from scraps of metal, wood and earth to a fully functioning machine shop in a post-apocalyptic scenario. And if you add in Herbert and Lou Hoover's excellent translation of De Re Metallica you're well on your way to having a blueprint for rebuilding humanity's pre-WWII tech base from scratch.