03-08-2010, 05:27 PM
Doing some sheetmetal work on an old mustang. Learned allot about heating, warping, blow-thru, etc. I've gotten better, especially my confidence level, but there's one area that I find troublesome; butt welds. Both sides of the sheetmetal has a tendancy to pull up through shrinking and contraction after it cools. My welding is good, good penatration, minimal heat zone, but like clockwork the two pieces will warp just a little immediately adjacent the weld. Often, I can't get behind the pieces to provide support or an opposing weld to anticipate shrinking. I recently set a door gap on a quarter panel with a relief cut, welded, ground, looked great! Then...... Sure, less than a 1/16" of bondo will cover the prob, but how do you prevent it in the beginning?