

Chemistry, math, physics, optics, metallurgy… The thing that is hard is how your needs for knowledge will change over time and what is accessible to you at each stage.
For general electronics, The Art of Electronics is the goto book. For actually understanding practical stuff, you need to build a knowledge of the industrial revolution and how it evolved. The inventions of James Watt opened up steam. The Bessemer process scaled iron. Large heavy castings drove the potential for large lathes, but lathes are the key to everything. A lathe is capable of cutting a more precise screw than the one used to operate it. That old screw can be replaced with the new, until you achieve your desired precision.
A reference flat is made using two granite stones rubbed together with water in between until the top one creates suction that can lift the other.
Prussian blue and hand scraping are used to make machine flat surfaces.
Automotive suspension components like springs and torsion bars are a good source of cheap tool steel. Engine heads are a good source of casting scrap and quality hardware. Wipers, window motors, and starters are great for building machines. Understanding how to repair and diagnose this stuff is a major skill. Knowing how to make real controlled heat is fundamentally important.
I’ve never encountered single sources for this stuff.









Becoming a roadie and riding a bike everywhere for years fixed me feeling like this. I had to get over all of my insecurities being in public in a cycling kit. Being around other people riding and racing, it became my normal. Now… I don’t have to look at me, so why the fuck should I care what anyone thinks. They are used to it or whatever, who cares. I’m more interested in inferring their real intelligence versus narcissistic stupidity based on their responses. Old people are all ugly. “For your age” is just an excuse for it. The vanity is boring. People who are judgmental are just projecting their own inadequacy and internal misery.