A shop story you already know
Old speeds-and-feeds rules of thumb were mostly about what the cutting tool could survive. Carbon-steel tools couldn't take the heat, so you ran slow. High-speed steel let shops cut much faster. Carbide pushed it further.
The metal didn't change. The tool changed, and the right number moved with it.
The guy who learned on carbon steel and kept running carbide at his old speeds isn't being careful. He's leaving most of the machine on the table, and calling it craftsmanship.
For each idea below: watch the video, read the article, then do the exercise. The exercise is where it sticks.








