In the pipeline industry, I believe DOT does not allow mig welding. To hard to control penetration. The have very specific specifications for root, fill, and cover passes. All in the name of safety. They do recoagnise the value of MIG in qualified hands, just that percentage of failures when welds are X-rayed is much higher on MIG.

Now, lets consider what we are welding on the jeep. Lets thing about the mechanix of the connection. The frame would be considered a butweld if you are repairing a cracked frame, So I would highly recommend the stick for welding it. For allmost all other welds on a jeep, rollbars, tire carriers, Frame repairs if you are plating it, etc. the welds are such that additional material can be deposited to create strength. If the steel has been properly beveled in preparation for welding, a small 120v MIG machine can fill the chamfer and melt both base metals for the first pass. On the second pass, a deep puddle can be generated that ties all three together, both base metals and the earlier weld. Thicker steel requires more puddling for deep penetration. With a 120v machine, 1/4" steel is probably the upper limit. Two of the more critical aspects of welding are adhesion to base metals, and sufficient cross-sectional area to be as strong or stronger than the base material. Both of these are obtainable with a MIG if care and patience are excercised.

[img]images/graemlins/tongue.gif[/img] Pretty good explaination, jfralph. It was actually quite a few years before industry trusted MIG welders on really critical stuff because there WAS quite a variation. I'm not much of a second-pass fan when it comes to MIG welding. I chamfer the seam, and weld in one pass if at all possible; "working" the wire, "sewing" the two pieces together and building the cross-section as I go. I'm talking here about 5/8" and 3/4" plate as on a trailer hitch bit or some such piece. [img]images/graemlins/crazy.gif[/img] If I'm butt welding pipe for a rollcage, I try to put a "chill ring" inside the seam so I can weld up against it and use more heat and get more cross-section. A chill ring is a section of pipe that you slit along it's length and reduce the O.D. enough to slip INTO your pipe at the seam. [img]images/graemlins/tongue.gif[/img]