Oct 13, 2020· An excellent heavy-duty die grinder/cutter, etc. is the RotoZip. The one I have is a single speed 30,000 RPM (revolutions per minute) unit that pulls 4 amps. At 100 percent efficiency, that roughly translates to 120v x 4a = 480w / 746(w per hp)= .643 hp and That's more than plenty. Aside from stones, their heavy carbide tips are nice.