LOL, not copper deposits. That's what happens when you do a fillet weld and some goo made it's way into the joint before you started to weld. Makes a nasty spatter mess :{ On the gas lens, the black crap is the result of touching the filler rod to the tungsten. Makes a heck of a pop when that happens

I've got a much more steady hand now
As far as the tungsten extension... ... On the pointed electrode, I set it that way when doing a fillet joint so I can use the cup as a guide to maintain the proper arc length and bead height. Also makes it possible to rock the cup along the workpiece to create the nice looking "stack of nickles" I've found with the regular type nozzles that more than about 5mm extension makes for trouble. Any longer and then gas cover will be reduced due to the cup being too far away from the work. Also, when welding around corners, it allows air to get sucked in behind the arc which really makes a terrible mess. Too much extension will cause the tungsten to oxidize more easily after you stop welding too.
The gas lens, however, is a totally different animal. You can have the tungsten hanging way outside the cup with no problem. I had it sticking out about 1. 5 inches once to reach into a joint. The gas cover is larger and much straighter. This makes corner joints and strange angles much easier and won't suck air behind the arc. One disadvantage is that the gas lens is a lot fatter than a regular cup, which can make it impossible to reach into some joints. Another is that it weighs about double what a regular cup and collet body does.
Sean
BTW, a Millermatic 175 made its way into the garage today

I know, I know... ..... plasma
