Welding burn thru

More of an art than a science - discuss metalworking and welding here.



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PostPosted: Tue Nov 16, 2021 11:47 pm
'68 Coronet R/T wrote:A lot of good information there.

Bottom line for your particular situation is to cut that portion of metal out and make a patch to weld in.

Think about your patch and the placement of your seams. Try to get the seams located where you have good access and sufficient metal for welding. Make your patches to fit nice and snug into the openings as well.

I found it much easier to learn proper welder setting by practicing on odd pieces of metal.
Start with the recommended settings for your welder on that thickness of metal and see what you get. A porous mound of metal may require more heat or less wire feed.

There are videos out there that go into detail on setting up a MIG.

I've already have my donor patch. Just need the time to install it.



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PostPosted: Thu Dec 02, 2021 10:41 am
Well its been a while How did it turn out?
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Fri Dec 03, 2021 12:43 am
20211202_212530[1].jpg
Well I wish I had more time! Anyways, I'm showing two pics. One of the donor piece. The other I've marked with thick black line where I think I will cut out. I am no expert. I appreciate any advice. Thanks.
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PostPosted: Fri Dec 03, 2021 8:19 am
Best advice I can give it to cut it out, with an extra margin of metal, around 1/4-1/2 inch. Then sneak up onto it with hand snips. Maybe final "shaving" to get it perfect, with a 2 or 3 inch sanding disc on an angle grinder, or hand file.



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PostPosted: Fri Dec 03, 2021 9:10 pm
I like body saws such as this:
https://www.harborfreight.com/high-spee ... uDEALw_wcB

Then over lap both the patch panel and the panel needing repair, Then cut both at same time with thinnest cutting blade available to get perfect cut line that matches.Then Try to get gap to zero gap OR as close as possible by filing the cut line using a file as Necessary. When I use a lot of patients I can get close to zero gap. then Tig weld or Gas weld a fusion weld. with zero filler rod is goal. when done correctly with a Tig welder you have perfect repair requiring little to no hammer and dolly work with little to no filler required to hide the repair.

A Mig can be used but keep the welds to a Zap zap zap a million times deal Not really welding in my opinion. Puts more heat into panel requires more hammer and dolley work over heats panel and bead is harder than Gas or Tig welding.
Dennis Barnett
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Sat Dec 04, 2021 11:57 am
It's going to be mig and hopefully I won't burn thru this time....

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PostPosted: Sat Dec 04, 2021 4:09 pm
I use a rotary cut off wheel.
Get the good ones and they will last a while, cheaper and they disintegrate. I get them 1/16" x 3" and have an arbor to mount them on that has 1/4" shaft.

Here's one similar to mine, except I don't by Harbor Freight Junk anymore:

Cut Off Tool.jpg
Cut Off Tool.jpg (26.15 KiB) Viewed 1006 times


I trace the outline of the patch and then stay inside of the line when cutting.
1968 Coronet R/T


ACTS 16:31



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PostPosted: Mon Dec 13, 2021 11:43 pm
20211213_203221[1].jpg
I welded my donor piece in. Few spots to touch up yet. I was happy the way it fit. Tried to take my time so it wouldn't shrink but no luck with that. It shrunk along the vertical bead. I tried to hammer and dolly it but it was awkward to get in behind. Any suggestions? I hate to fill it up with bondo.



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PostPosted: Tue Dec 14, 2021 9:20 am
It's an urban myth that there are ways to keep metal from shrinking when welding. You can minimize the effect, but any time you melt metal, it will shrink as it cools. Your vertical section is the flattest, so that's where it "shows" the most. Nothing short of hammer ON dolly work will stretch it. If there's an interior piece in the way, cut it out, to get access. Interior metal doesn't show, so if it gets 'wonky' when welding it back in, it's not that important.



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PostPosted: Wed Dec 15, 2021 1:25 am
So I'm still trying to learn from the shrinking issue. The replacement piece fit tighter than looser, if that makes sense. If I had more gap, mite it not shrink so much? Metal had no where to go as it expanded then shrunk inwards? Still trying to figure it out for next time. If I cut metal out of the box to access for hammer and dolly work, I'm worried about opening a can of worms lol...
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