I'm confused - My Miller Migmatic 171 150 Amp weldor's amp control knob has 6 settings, I assume 25 Amp per setting.

When tacking 1.6mm square tubing, I'm following Mark's suggestion - turning machine to full blast. That works fine.

When fully welding I found that at setting 5 (125 Amp?) I need to move very fast and am more comfortable at setting 4 (100 Amp?). At setting 3 (75 Amp?) I've got doubts whether I get the penetration/fusion that I want.

With my TIG, I set it to 50 Amps and do a solid weld, sometime I even go down to 40.

What can explain this difference. Oh yeah, I'm using CO2 with the MIG so that's even hotter.

Its all to do with the amount of material you are melting per second. A 1" pass with a mig takes about 2 seconds, but with the tig you could be there for 10 secs, so less amps required

That sounds perfectly reasonable.

Thanx Mark