[sfink]

That makes sense. With (strong) steel maxxing out at around 1Gpa, that's 4 orders of magnitude less. The rotation frequency gets squared, so... 10Khz? Huh: "The fastest rotation achievable by standard motors is of the order of 10 kHz". (How does a "standard motor" achieve 10 KHz without ripping apart, then? I don't think many standard motors are 5mm or smaller.)

Thinking about this makes me imagine a potter's wheel for shaping a ductile metal. It spins really fast, but you can only reshape in the outwards direction, and the resistance goes up dramatically towards the center. Oh, and if anything flakes off, you're dead. But before you die, you could probably make some pretty artwork.

[jmb99]

I’m not an expert, but I don’t believe there are that many motors that spin at 600k RPM (= 10kHz), and definitely no large ones. That is absurdly fast. Modern turbochargers are some of the fastest-spinning off-the-shelf things your average person can buy, and they normally top out below 200k RPM (and only the smallest/lightest turbines can spin at 200k RPM). If there does exist a 500k+ RPM electric motor, I would be surprised if it was larger than a few mm.