Ran a practice butt joint on some 304SS exhaust tube( 2.25" OD/.065" wall ), to get in some practice time with my new HTP Invertig 251. Could be worse, but a LOT of room for improvement. Maintaining a consistent bead profile with .040" filler is a sonofabitch! Got decent melt through at 50A, but will bump it up a couple of amps next time. The 5 cfh back purge was sufficient to prevent sugaring. Used a sharp 1/16" C-K LaYZr tungsten, and Fupa 12 cup, and 35 cfh.