Allan,
No filler on the right, filler on the left.
![](http://img.photobucket.com/albums/v377/thirdeye2/welding01/dsc04505aL.jpg)
I'm not really getting undercut, more like a wash with a reduction of thickness...which is typical of tacking, and is what I sort of expected. I did get some burn back and serious deforming due to the heat on some of the sample welds. I am using a tight fit and have a simple jig that works for most of the connections. I also tried pre-placing the filler. It sounds like playing with different methods using the pedal is in order.
Back to one of my questions, what amp range should I be working with.