I had the pleasure of operating some machines like that too. One was a hydraulic shear roughly the size of a school bus, and once you stomp the pedal there is absolutely no taking it back--it'll do a cycle and nothing can stop it. We also had a Buffalo Iron Worker which I managed to misalign a punch in once. A hefty chunk of HSS flew ~100ft across the shop and embedded itself in the steel siding. I don't know how it didn't hit me, because I was at the time occupying much of the solid angle. However the machine that scared me most was a giant drill press from the late 1800s that had a ~4' cast iron gear on top of the drill shaft which held enough inertia to keep the drill spinning for about a minute after the power was shut off.