i havent used it on the back the earth goes to the metal on the front and cut with the gun other than plugging in the air from the compressor thats all ive used on mine
ive cut right up to 10mm severance cut at 40 amps and a higher setting for air
You don't need to use the earth nut on the back of the machine. The machine is earthed through wiring to the earth in the plug. Don't confuse this with the workpiece return on the front which people often call the earth too.