Kevin West used a big plumber's tubing cutter I think. (I oughta try that one from Granddad's tool chest)
I use a chop saw and cutoff wheel, then jam the tube up against a silver-deming bit larger that the OD and debur the inside. Hang on tight with leather gloves.
Bench grinder for the outside. Kinda archaic, but gits the job done. Might try the metal lathe next time
Turtle, slow