I think the inherent problem using a very small torch is that in order for the weld pool to become molten, the small heat source has to stay in one place a long time. Natural heat transfer starts to distort the adjacent metal.
If you have a much larger source of heat (concentrated) the pool becomes molten and the weld completed very quickly. This precludes the adjacent sheet metal from heating and warping.
This sure sounds impressive...I wonder if it's valid?
Edit: Digging around through my crap today I noticed that the little torch I have is indeed a Smith Little Torch!
Stuart
