Comments by "Scott Franco" (@scottfranco1962) on "The Mind-Blowing Machines that Stamp Millions of Metal Parts - Smarter Every Day 288" video.

Besides the fact that pretty much any complex item of sheet metal is made by stamping, you can always tell how the part is made by looking for the "signature" of stamping on the edge. This is a unique pattern left on by the stamping where half of the edge looks one way, and is a different color, than the other half. The reason it happens is because when the die is punching out a section of the material, it will compress the metal until it reaches about half way into the sheet. At that point the sheet metal will give way and essentially "fracture" as the punched out material rips away from the stationary part of the sheet metal. Stamping is an amazing process that goes back into the 1800s. It essentially enabled mass manufacturing of a lot of goods. The dies were made by hand, and many or even most still are. A die is carefully fitted by a die maker, and then stamps out hundreds or thousands of parts at high speeds. And then they wear out and need to be repaired or replaced. Its been the way heavy industry is done for more than 100 years.
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