Welding burn thru

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



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PostPosted: Thu Oct 21, 2021 12:42 am
I'm a fairly new welder. I'm better at laying beads than trying to spot weld on my trucks rear quarter panel. Long story short, I created a burn thru hole that I am trying to weld up with no luck. Even tried a home made heat sink but can't reach in behind to make it work properly. I cut my wire on each try and make sure the surface is prepped and clean on each pass. I have a Miller 211 and using .023 wire. Since I can't reach in behind well enough, is the quality of the old, probably slightly rusty and dirty metal that much of an issue? I watch lots of guys prepare patches and butt weld them in with no consideration of the metals backside. Any suggestions, or do I need to just practice more lol. Thanks for any advice!



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PostPosted: Thu Oct 21, 2021 12:50 am
Tried to post a pic but it's telling me my file is invalid? What ever that means lol.

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PostPosted: Thu Oct 21, 2021 1:31 am
Read this if you haven't already: viewtopic.php?f=8&t=14600
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PostPosted: Thu Oct 21, 2021 10:22 pm
20211020_162312 Cropped spot weld 79 ford.jpg



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PostPosted: Fri Oct 22, 2021 7:27 am
Is that a brazing repair that is gold-ish colored on that? If so welding near it is going to be a real problem. Cut it completely out and make a patch to replace it. As for welding up a hole, without a backer? Practice, experience is what it takes. Put light tacks around the edges, than fill in the middle, but it's much harder doing it, than explaining it.



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PostPosted: Sat Oct 23, 2021 9:34 pm
chopolds wrote:Is that a brazing repair that is gold-ish colored on that? If so welding near it is going to be a real problem. Cut it completely out and make a patch to replace it. As for welding up a hole, without a backer? Practice, experience is what it takes. Put light tacks around the edges, than fill in the middle, but it's much harder doing it, than explaining it.

It's not brazing, just reflection I guess. Anyways, I kinda got it working better. Turned up my wire speed which helped a lot. I'm creating some good dots. The only trouble is, I've burned thru so many places that I can't really get a heat sink back there to build up the holes, if that's the right terminology... I think I'm going to have to replace a section now.



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PostPosted: Mon Oct 25, 2021 6:01 am
Could that area be thin enough to have needed a patch?



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PostPosted: Thu Oct 28, 2021 1:17 pm
When trying to fill holes with Mig and grinding gobs and mess down:

Its been my experience that filling or build up a Blow out hole area even with a Copper heat sink to be a Bad repair. Better to cut area out and weld in new metal is my best advise. I use Unibits to cut round holes and cut patches out with a Punch tool for small holes. I have punch tools a dies from 1/4" up to 9/16" I thank Chevman for this Idea that works extremely well.

A Mig wire Filler weld repair is a very Porous repair with lots of hairline cracks and micro holes or voids for a lack of better terminology or explanation.
(After grinding mess down look at metal with Hi power Magnifying glass!)
You will see These cracks and voids they will hold moisture, Moisture from the air itself and come back to haunt you as they begin to rust fairly quickly even when sealed up.

If you do this type of repair make sure to clean up back side grinding down mess as well as top side clean with Alcohol and then Acetone or MEK as well as you can then coat back side with Epoxy and then top it off with Fiberglass filler Too keep moisture out. Do the same for outside.

This is not a Good way to repair sheet metal and we are all guilty of it at one time or another and I am not saying I haven't done it myself but the repair is not strong, it is not clean, and it will rust even if covered correctly its just a matter of time.

I have tried Metal treatments after grinding and coating with Zink with good results so far? Its a Time thing though like I said, it will go bad its just a matter of time.
Its a bad repair type and should be avoided if possible.
I get it that not everyone has all the tooling that I have and not all welding projects need to be text book perfect.
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PostPosted: Tue Nov 16, 2021 1:38 am
Doright wrote:When trying to fill holes with Mig and grinding gobs and mess down:

Its been my experience that filling or build up a Blow out hole area even with a Copper heat sink to be a Bad repair. Better to cut area out and weld in new metal is my best advise. I use Unibits to cut round holes and cut patches out with a Punch tool for small holes. I have punch tools a dies from 1/4" up to 9/16" I thank Chevman for this Idea that works extremely well.

A Mig wire Filler weld repair is a very Porous repair with lots of hairline cracks and micro holes or voids for a lack of better terminology or explanation.
(After grinding mess down look at metal with Hi power Magnifying glass!)
You will see These cracks and voids they will hold moisture, Moisture from the air itself and come back to haunt you as they begin to rust fairly quickly even when sealed up.

If you do this type of repair make sure to clean up back side grinding down mess as well as top side clean with Alcohol and then Acetone or MEK as well as you can then coat back side with Epoxy and then top it off with Fiberglass filler Too keep moisture out. Do the same for outside.

This is not a Good way to repair sheet metal and we are all guilty of it at one time or another and I am not saying I haven't done it myself but the repair is not strong, it is not clean, and it will rust even if covered correctly its just a matter of time.

I have tried Metal treatments after grinding and coating with Zink with good results so far? Its a Time thing though like I said, it will go bad its just a matter of time.
Its a bad repair type and should be avoided if possible.
I get it that not everyone has all the tooling that I have and not all welding projects need to be text book perfect.


Thanks for the advice Dennis!

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PostPosted: Tue Nov 16, 2021 2:18 pm
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.
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