It was only a small break really, as i said the guarding contained it all.
The biggest bumps I have seen were 2 in the same plant during commissioning stages.
For one I was working on the machine along side, my colleague loaded the part and hit the 2 hand cycle start.
The machine set off and then there was a gut wrenching carumpf noise and a plume of smoke and dust, the machine went quiet.
The (cam) shaft he had loaded had missed a prior op, thus it was not ready for grind, the carumpf was 6 off 1" approx wide 42", yes 42" diameter grinding wheels self destructing!
The wheels & spindle were over 1000kg, and took 16 man hours to change without there having been any damage.
It took 4 of us 12 hours to rebuild the machine, and we were the machine builders service engineers.
We had a similar thing with a crankshaft grinder in the same factory, but that was auto loaded and there was no one nearby.
I had the clients operators, tradesmen & engineers wound up may a time by diving for cover after hitting cycle start for months after these incidents.
Oh, no bits left the guards in either incident due to the design of the machines, but the wheels were primarily removed with a shovel!!!