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  #11  
Old 03-08-2013, 07:31 PM
foamcar foamcar is offline
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Pat
Thanks for the added tip. I have done that on some inner panels but am afraid to try it on this outer panel for fear of making conditions worse. So far, with grinding underneath it is coming along pretty good. I am showing pictures taken today where you can see the long weld. The forward part is finished. The part from the fuel door opening rearward needs to be finished.

Here are some close ups of the area needing finishing:
Not sure if I am getting these pictures in the right spots, so the 2nd on is the area needing finishing.
Next 2 are areas already done, so you can see how good or bad it is. Where the metal on both sides is new, the welds dress down much better than where there is old original metal.

Finally, some pictures where I have filled in the remaining gaps. Not my best welding day. Usually can get the beads flatter. Anyway, looking for constructive criticism, as am always trying to improve.

I did try a hotter setting and burned right through. Must not have been quick enogh on the trigger. But I abandoned that until I can practice on some old pieces of metal laying around.

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  #12  
Old 03-09-2013, 08:32 PM
olcarguy olcarguy is offline
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Remember when you go hotter you have to increase the wire speed to compensate for the added heat....
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  #13  
Old 05-10-2017, 10:53 AM
tjratz tjratz is offline
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What if you cant get the back side to grind due to obstruction(s)?
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  #14  
Old 05-10-2017, 02:26 PM
Mike Rouse Mike Rouse is offline
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You are in for a fight when you MIG weld sheet metal. Sheet metal, the type most commonly used in body work is low carbon having a yield strength of around 30,000 pounds per square inch. Strong enough for its intended use.
MIG wire ER70S-6, a commonly used type, has a yield strength of from 65,000 pounds per square inch to 75,000 pounds per square inch. When used to weld structural steel (A36 with a yield strength of 36,000 pounds per square inch) it will make a very strong weld which is great. But when ER70S-6 is used to weld low carbon sheet the weld will be strong too. So strong that it will be twice as strong in yield than the sheet metal. And this is where the fight starts.
I am nor saying that the results won't be acceptable. This just explains why MIG welded sheet metal butt welds are so difficult to work.
My preference is to weld with oxy acet and use tie wire for the filler if needed. The tie wire has a low yield strength and is quite malleable.

Mike
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  #15  
Old 05-10-2017, 02:43 PM
John Buchtenkirch John Buchtenkirch is offline
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What Mike says ^^^^^^^^^^^^^^^^^^^^^^ , tig or gas welding for me for any butt welded panels. Mig certainly can work though without nearly as much experience needed. ~ John Buchtenkirch
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  #16  
Old 05-11-2017, 12:17 AM
Oldnek Oldnek is offline
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I have been using the mig for mostly 90% of my work, butt, fillet, overlap, gap and no gap. I use .08mm Er70s wire, on Zincanneal and mild steel, from 1.6 to .008. and depending if I have back access to the back of the panel, is whether I use gap or no gap.
With the mig, there must be the right amount of penetration through to the back of the panel where you can't see any join line.
The technique that works for me is speed and higher heat settings.
If you do see that line your just wasting your time, as there will be no penetration of the panel and the weld is just sitting on the front face, which will then be ground down, Smooth!. Where once you start to planish it down it will crack and your back to square one. If your lucky and have not cracked it your panel will still be weak and with that secret line behind will create a moisture edge for corrosion later on.
Practice with Wire speed setting lower than voltage and work on weld speed, so pretty much your mig will be fusing like a tig more or less. But not that low where you get burn back at the tip.
As Mike mentioned with mig, the weld bead is harder than the parent metal so if you can keep the HAZ uniform and even, keep the weld constantly moving without stop starting, this makes the panel is very workable, comparative to tig and oxy. If you stop start, the panel is hot'n'cold which means more grinding and distortion. Others will have different views, but it works for me.
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Last edited by Oldnek; 05-11-2017 at 12:19 AM.
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  #17  
Old 05-11-2017, 12:20 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by Mike Rouse View Post
You are in for a fight when you MIG weld sheet metal.
My preference is to weld with oxy acet and use tie wire for the filler if needed. The tie wire has a low yield strength and is quite malleable.
Mike
yeh, tie wire / mechanics wire for O/A welds.
Old school.
Works as good on the Achafalaya as in West TX or MN or CA or NV.
Pretty universal, I'd say.

Thing is, youthsters better off doing connect-the-dots than hot planishing.

Generational translations notwithstanding.
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  #18  
Old 05-11-2017, 07:43 AM
John Buchtenkirch John Buchtenkirch is offline
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Painted & striped coat hangers was the other favorite of backyard welders in search of softer welds. I know 2 welders that swore by them for easy grinding. Surely coat hangers are not held to any metallurgical standards so the idea just scares me . ~ John Buchtenkirch
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  #19  
Old 05-11-2017, 10:11 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by John Buchtenkirch View Post
Painted & striped coat hangers was the other favorite of backyard welders in search of softer welds. I know 2 welders that swore by them for easy grinding. Surely coat hangers are not held to any metallurgical standards so the idea just scares me . ~ John Buchtenkirch
The real metal-men I worked with would sometimes use mechanics wire - but they laughed at coathangers as absolutely last resort, shipwreck sort of last resort. I never used any. We all regarded the coathanger guys as those who lived at the ends of the earth ..... and probably also sewed their own hide coats to hang on those hangers.

roll of mechanics wire
P1030712.jpg
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  #20  
Old 05-11-2017, 11:11 AM
Mike Rouse Mike Rouse is offline
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I use this 16 ga rebar tie wire as filler rod. It weighs 3.5 pounds per roll and costs around $5. To prepare it for use I first unroll alength of about 15 feet. I attach one end of the wire to the vise on my workbench and grip the other end with vise rips and pull on the wire. This will straighten the wire. Next I cut the wire to usable lengths and place them in my rod holder.n

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Last edited by Steve Hamilton; 05-11-2017 at 12:36 PM.
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