My surface grinder is reasonably well shielded to absorb such mayhem. Once I was working near a surface grinder that the operator pushed too hard, fragmenting the wheel. One large chunk thumped loudly into and dented the steel door about 50' away. The rim velocity is ~60MPH. I count myself lucky to not have more vivid tales of sharp flying machine fragments, though I have been spattered with another machinist's blood and finger parts.
It's informative to helplessly watch a piece of equipment shake loose and fall off your motorcycle at that speed. I had a can of soda burst like a grenade when it hit the asphalt below my boot. jsw