The many, many manufacturing processes listed on Wikipedia #makerbusiness
If you ever wanted to see a category tree of over 300 manufacturing processes, look no further! There is a lot to be learned spending time in this rabbit hole, which even for Wikipedia is an exhaustive category.
Get lost comparing the virtues of full-mold and lost-foam casting, or learning about ultrasonic welding (so cool!). The page has many of these esoteric and artisanal methods of manufacturing, but also lists things as basic as fasteners (screws and the like).