We should have a thread on this board that has links to some of the many resource sites for learning about materials, machines and machining techniques, tips and tricks.
So, I'll start it off with one of my all-time favorites, from a fellow that used to be a regular with us in the much earlier Steam Forum World, though he disappeared from our fellowship some years ago, but who has created many wonderful projects, and shared them in a way that all could learn from. Some of the projects were steam engine builds, and some of them were for building accessories for our machine tools.
Having learned much from him my-own-self, and having successfully built from a couple of his tutorials, I will recommend Dean Williams and his website to you all: