My University Bike Lock Design - Youtube Video

the material stops a chain saw at full revs pretty quickly
bigger grinder = same result
it'll just mess up the motor on the grinder before it has a chance at getting to the chain
the type of chain being used is pretty important
what spec is the chain ?

I'll believe that when a 3rd-party tests it. It doesn't look like there's not enough material to stop a decent grinder.