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Old 11-28-2018, 05:41 PM
RB86 RB86 is offline
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Join Date: Nov 2018
Location: Charlotte NC
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Quote:
Originally Posted by RockHillWill View Post
Just to add one of my limited experiences with a problem with MIG welding. Prior to getting acquainted with gas welding, I restored a December 1931 Model A pick up with the then new style steel roof. It had very bad drip rails on both sides. The restoration shop that I used had a P9, a fabricated wheeling machine and an Eckold. I thought this was the shop to use, but as I got more into the restoration, I became disillusioned when they wanted to MIG weld the drip rails to the roof section. I had seen many issues with MIG welding while racing the stock cars but wrote it off to being 'rough service life'. They proceeded to over ride my input, but it turned out very nice. That particular truck was entered in five national events and won all five of them, and I was still thinking I did a good job, but after that fifth event I sold it to a Model A collector who took it to a show in Hershey and won some sort of a national award, but merely weeks later the roof cracked on both sides and the buyer was livid with me and I had to dance like hell to avoid a lawsuit. NEVER again for me! Since then I have paid attention and it very common to see cracks in MIG welded sheet metal welds.

This in only my opinion based only on my experience and observations.
Will Ive done my fair share of sheet metal mig. What happens I've found, when you stitch weld the panels together, basically pulse and overlap tacks in an effort to keep it cool, it doesn't penetrate as well as a fusion weld. Then you go to dress it with the grinder and if you go too far, you can see the hairline joint under the welds.

Then planishing those joints are really asking for a crack. Here's some fenders on a 1950 Willy's truck I'm working on. I widened them 5 inches and then extended them 14 inches. We back the joint with a product called metal to metal afterwards, which dries incredibly strong and is sandable. It's not as ideal as a Tig or gas weld with nice planishing done, but the budget and timeframe didn't allow me much time to take it to that level.

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Rob
1950 Cadillac
1956 Cadillac
Looking to build my own car from scratch
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