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Old 04-17-2011, 07:42 PM
JohnStubbe JohnStubbe is offline
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Default Sheetmetal welding?

I've been wondering about different sheet welding techniques. I was wondering concerning mig, but any info on Tig or oxy would be cool too. So here are the point, and what way do you guys do it.

- do you gap out the metal or go for perfect tight gaps (also do you try and 45 the two sheets so they lay together flat)
-Do you stitch, run beads,multiple tacks in a row, or single tacks and work around the panel.
-Do you put rags on the metal to reduce cooling, quench welds with water, blow gun cool them, or let them cool naturally
-Any body back welds with copper or leave it open.

I tend to gap out the panels about a air saw blade width, weld an inch or so of little tacks (buzz,buzz,buzz,buzz right after each other, the helmet doesn't even turn off. Then grab a blow gun and cool the weld after a sec or two.

My thinking is the gap lets me put less heat to get penatration, the tacks just slow it down since worm welding with mig seems to be a crapshoot as far as penatration (sometimes its perfect, other times its cold or burned through). Also I don't like using water or even air super quick as It seems to make the weld harder to stretch and bump back later. The air is mostly so I don't have to wait to do the next weld or worry about the whole panel warming up.

I'm really interested in how to weld up a seam strongly that will be formed extensivly later and not crack.

So what do you guys do? Does it warp bad, welds crack later ever, hard to form?
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Old 04-17-2011, 08:59 PM
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Joe Hartson Joe Hartson is offline
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John, there is a lot of information already on the site. Search is you friend. I would suggest that you look around the site and do some reading before you start asking a lot of questions.

Here are a couple of links to threads that will get you started, there are a lot more threads on welding.
http://www.allmetalshaping.com/showthread.php?t=409

http://www.allmetalshaping.com/showthread.php?t=902

http://www.allmetalshaping.com/showthread.php?t=993
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Old 04-18-2011, 06:50 PM
A Glause A Glause is offline
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John
I never mig anything that is butt welded, just me others do and have good success. I tig for speed but will oxy weld too. Just depends on the job. David Gardiner is on this site check out his tech.
Andy
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Old 04-18-2011, 07:09 PM
weldtoride weldtoride is offline
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Welcome to the forum from Illinois.

Quote:
Originally Posted by JohnStubbe View Post
.

I'm really interested in how to weld up a seam strongly that will be formed extensivly later and not crack.
You could probably ask three different guys here and get four different answers to that one. As mentioned above, Search is indeed your friend; trial and error on scrap panels is even more valuable. Personally, MIG would be my third choice for a panel that was to be "formed extensively" afterward. O/A and TIG first and second. Both with no-gap butt welds, as little filler as possible. That's what works for me. I am sure you will hear differing opinions, that's one of the functions of a forum.
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Old 04-18-2011, 09:55 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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I'd agree. MIG is too brittle a weld for extensive shaping after the fact imo.

OA or TIG would be my choice.

That said, I'm not sure MIG WOULDN'T work but I don't think it'd be very satisfactory. MIGing in patch panels that are going to have a skim coat of plastic over them is one thing. Trying to shape MIGed panels is something else. It can be done. I've seen it when we did Bennett Chapman's truck up at Dutch Comstocks but the work after the welding wasn't 'extensive shaping'.
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Old 04-18-2011, 10:41 PM
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Marty Comstock Marty Comstock is offline
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Totally possible to do significant shrinking and stretching on a mig weld. More time will be spent grinding, and practice will need to be had to get good with a mig to do it. Wouldnt be my first choice, but far from impossible. Just not the easiest or quickest of choices.

Marty
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Old 04-19-2011, 12:59 PM
David Gardiner David Gardiner is offline
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I am with Mark (above) on the order of preference of the welding methods for butt welded joints. Mig will tend to crack if you work it extensively - Just so I don't get jumped on - note the use of the word tend it may not aways but it has a tendency to.

For me tig is a little awkward a lot of the time so I prefer gas. I cut my sections so they match each other and run the joint in with little or no filler rod to cut down on distortion.

David
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Old 04-19-2011, 06:20 PM
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Get my 2cents in here, since joining this site a couple years ago my sheetmetal weld skills have gone thru the roof - i am not as good as the guys that just gave you advice, but i am good enough to advise you to listen very close to what they say and do as thy do.
I tig and as David described i get the butt joints tight, i fuze the metal and have filler rod handy in case the seam spreads and i need to dab. For the most part i have both hands on the torch and moving rapidly. It is fun.

Post up some pics under the sheetmetal welding thread that is an ongoing thing and maybe we can give up better advice.
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Old 04-19-2011, 11:37 PM
JohnStubbe JohnStubbe is offline
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I know what you mean about the Tig and gas. Thats what we used primarily in school. Its so much softer and workable, plus less grinding. I've just seen lots of people use the other techniques I mentioned about Mig. Just wondering what is true proven technique and what is just peoples habbits.
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Old 04-20-2011, 12:50 AM
David Gardiner David Gardiner is offline
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John the technique I teach with gas welding is one that was used on coachbuit cars since the twenties, I have seen welds done in this way on cars that I have restored from that era so its a petty proven technique.

David
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