I am aware of the maximum safe rpm = 9000 / diameter rule (guideline?). I usually take no notice of that and use the crank up the speed until it vibrates, empirical algorithm.

My question is this: what is the logic of the rpm=9000/D? Who came up with it and is there any valid physics behind it? Seems more of a one size fits all, bureaucrat solution. Also, not all lathes have rpm indicators, and each chunk of wood is different.

TIA, have popcorn and awaiting physics lecture