I have found 2 things in my year or so of ownership.
1. Grind down to bare metal for a ground and this thing cuts like a Jedi Light Saber!
2. At 20 Amps you can get away with just eye protection but at 50 amps that will give you a white raccoon mask around your eyes and a very burned face and forehead . It even can get under your hat since the arc is coming from a low point.
Thurmond