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When I made the Hand Tools category, I was thinking of some processes that don't strictly fall into the other categories that exist right now, such as filing and grinding. Admittedly I'm not sure if we need a page for these processes or if we should choose a different name. (maybe Metalworking? that seems too broad...)

As for the categories Emily mentioned (Additive, Sheet Metal, Injection, Composites), I think they make sense.

I also think we should add a PCB or Electronics page.

PCB is a good one that I didn't think about before. Perhaps we should name it something specific such as "PCB manufacturing" and talk about laminating, traces, masking, etc and list low quantity PCB suppliers? PCB design is a whole other animal that should have its own page.