Incidentally, I had the opportunity to try using helium as a shielding gas for the first time last week. It was pure helium and I dont have a gas mixer. The results were... less than spectacular. That exercise was purely academic and pretty much for grins. If it became necessary, I would definitely use a helium/argon mix. The welds were ok once cleaned up, I tried both DCEN and AC. There is a pretty good thread over on WW about using DCEN with helium for aluminum, so I just had to try it. They have a couple of nice miller helmets at the shop, but something about the tint of the lens I don't like. I just knew that I needed a four sensor helmet and bought the first one the tool guy could produce and so far so good.