For the metal working enthusiast here are a couple of volumes that together constitute an excellent course in machine shop work and general metalworking. The emphasis is on machine shop work but also covers to a lessor degree, shop drawing, machine building, casting, forging, sheet metal, welding, machine hydraulics and most other aspects of metalworking. There is also some math, to the degree that would be expected of most machinists, without getting to deep into the theory.
You can treat it as a source of good practical information or use it as a instructive course in the discipline, with questions to test your knowledge at the end of each subject, and answers at the back of the books.
First published in 1971, before computerization, but still very pertinent for most home shop level work.
To download "Mechanical Engineering Craft Studies Part 1 and 2" go to my Books - Free Downloads page. Both are djvu files, 5 MB each, #'s 35 and 36.