Welding holes

c.moo · Jul 3, 2020

Butt welded trunk pan in , grind welds down , put light under trunk to see where pin holes is . problem is when i weld pin holes up it gets one be side of it not getting anywhere . Try turning heat down but then i get mounds where it isn't hot enough . Need advice . Thanks

khryslerkid · Jul 3, 2020

Find yourself a piece of copper or brass and hold it on the back side. I'll even use a light smear of nozzle dip on the copper/brass to keep it from sticking. It has wax in it.

Bad B-rad · Jul 3, 2020

Photos may help.
Teaching proper welding techniques over the net is difficult.
Is metal rusty? If not clean and rust free it will give you ****.
Is shielding gas on?
Also with a mig its sort of a on---off----on---off type of trigger pull on the gun, you cant run long beads. Just a series of overlapping spot welds.
When welding sheet metal with mig point the wire toward the thickest part of the metal,(your mounds) and quickly weave toward hole.
This keeps heat in thickest part of metal to avoid the burn thru.

You can also try copper or aluminum plate behind the holes your trying to weld, as weld wont stick to copper or aluminum, and allows you to fill the hole.
Hope this helps

Bad B-rad · Jul 3, 2020

Getting your voltage and wire speed correct, is most important, next its really just practice, practice, practice.

You may want to grab some scraps the same gauge as what your trying to weld, and practice on that for a bit, that way you don't care about your mess ups.
After a bit, you'll get the hang of it!!
Good luck!

hoover · Jul 3, 2020

I know it msy seem obvious, but copper,brsss, and aluminum are sll good conductors of heat.
Hold it with a pliers or it may burn your hand

c.moo · Jul 3, 2020

Bad B-rad said:
Photos may help.
Teaching proper welding techniques over the net is difficult.
Is metal rusty? If not clean and rust free it will give you ****.
Is shielding gas on?
Also with a mig its sort of a on---off----on---off type of trigger pull on the gun, you cant run long beads. Just a series of overlapping spot welds.
When welding sheet metal with mig point the wire toward the thickest part of the metal,(your mounds) and quickly weave toward hole.
This keeps heat in thickest part of metal to avoid the burn thru.

You can also try copper or aluminum plate behind the holes your trying to weld, as weld wont stick to copper or aluminum, and allows you to fill the hole.
Hope this helps

No rust , shielding gas on , no long beads , short off and on and off blast spot welds . Will try copper backing , These are pin holes not big holes . Just going to have to find sweet spot for wire speed ,etc.

Demonic · Jul 3, 2020

If the pin holes are too close together, it's chasing your tail. The heat needs to go down as you weld in the space of nanoseconds. Hard to do with most Migs. As others said above, practice on scrap rusted metal with similar pinholes. High end Tig machines are better at this, but often the most economical solution is to cut out pinholed section and install solid 18ga that you can weld.

moparlore · Jul 3, 2020

I tell the guys at my shop that it takes literally miles of welds to make them right. Practice, practice, practice, and then practice some more.

eldubb440 · Jul 3, 2020

the original metal or the replacement metal? ……… sometimes the new metal is just ****

Bad B-rad · Jul 3, 2020

When I wanted to learn to weld, my dad started me off with 7018, and told me, if I could learn to run this rod out of position, I could weld anything.
I was welding for 5+ years before I ever tried a mig, lol
A good tip for beginners to learn how to set voltage and wire speed correct, is make it sound like bacon sizzling in the pan, and your there.
Once you get some welding time in, you will know when it needs more of one and less of another.

One more thing you can check is the size of the wire, your running.
If your trying to weld sheet metal with .045 wire, it will be more difficult then .030, it takes more heat to melt the thicker wire.

Builderguy · Jul 3, 2020

Brad B-rad is pointing you in the right direction. I use .024 wire for almost everything now. As others have said, use a copper backer. I don't know what brand you have but on my Hobart Handler 140 the power is at the lowest setting, the wire speed is at 50, and the shield gas is at 30 with trigger off. If the metal around the hole is too thin you will blow through, nothing you can do about that. You can try a few tricks: Put the wire a fraction of an inch above your pin hole and pull the trigger for just a fraction of a second. You are no try to weld , you are trying to fill the pin hole so you can build weld around it. I use a blow gun to cool my metal. As soon as I release the weld trigger I start pulling the air gun trigger. Not so much that you blow the metal around but enough to cool it very fast. Repeat, repeat, repeat, etc. You can also try to build the weld on a point a little ways away from the pin hole and work your on-off-on welding toward the pin hole, filling the hole, and then working past the hole a little. More grinding but less blow out. Last, but not least, put the tip almost in plane with the metal so you are welding sideways. Little harder to do this, but it works on thin metal as you have to blow thru a lot more metal vs welding straight down or a at a slight angle. What you are trying to do is build on the edge of the metal you just blew through. Then slowly build on your weld until the hole is gone. I can fill pretty big hole doing this. Good luck and don't forget to clean your ground area, makes your life a lot easier.

Jhn824 · Jul 6, 2020

c.moo said:
Butt welded trunk pan in , grind welds down , put light under trunk to see where pin holes is . problem is when i weld pin holes up it gets one be side of it not getting anywhere . Try turning heat down but then i get mounds where it isn't hot enough . Need advice . Thanks

So it sounds like your talking about the tiny pin holes in or beside your spot welds...not actual blow through..correct?..if this is the case....its best to get your pan completely welded in.. dress all your welds... and then start working on your tiny pin holes... spot them in dress some more..repeat.... its an exercise in patience... good news with a floor or trunk pan... if you dont get every single pin hole most likely your going to cover your seams on the inside with seam sealer. that will fill any that you miss.

c.moo · Jul 7, 2020

Right on Jhn824 ! Trying to get all pin holes cover the best i can . Heard of people get to this stage they use metal filler or fiberglass , etc. which i will to . I'll keep plugging away , Thanks everybody

747mopar · Jul 7, 2020

Bad B-rad said:
When I wanted to learn to weld, my dad started me off with 7018, and told me, if I could learn to run this rod out of position, I could weld anything.
I was welding for 5+ years before I ever tried a mig, lol
A good tip for beginners to learn how to set voltage and wire speed correct, is make it sound like bacon sizzling in the pan, and your there.
Once you get some welding time in, you will know when it needs more of one and less of another.

One more thing you can check is the size of the wire, your running.
If your trying to weld sheet metal with .045 wire, it will be more difficult then .030, it takes more heat to melt the thicker wire.

Yes, wire size is critical! I use .023" on sheet metal. As said running a larger wire requires more heat to get it to puddle, I typically run my amps a bit high so that a quick tack flows out and forms a bit of a bulge to grind on the opposite side.

Bad B-rad · Jul 7, 2020

I also like to run a bit "Hot" while welding, when I can. You can always adjust the mig gun distance from the work, while welding as an on the fly heat adjustment.
The farther back the less the wire will "bite" in to the metal.

C.moo, any chance you can post a photo of the issue you are having?
Just so I understand a bit better.

It sounds to me. like you may be running a bit low on wire speed, and not putting enough new material back into the weld.
There are two ways to fix this, one, add more wire speed, or two drop voltage.
This is where the practice comes in, to determine which move will best fit your situation.

It sounds crazy, but when you weld, you are actually pulling metal up from the parent material, toward the arc, that's why you need to add material back into it.

Hope this helped, I am sure with some practice you will nail it!!!

Jhn824 · Jul 8, 2020

c.moo said:
Right on Jhn824 ! Trying to get all pin holes cover the best i can . Heard of people get to this stage they use metal filler or fiberglass , etc. which i will to . I'll keep plugging away , Thanks everybody

Jhn824 · Jul 8, 2020

c.moo said:
Butt welded trunk pan in , grind welds down , put light under trunk to see where pin holes is . problem is when i weld pin holes up it gets one be side of it not getting anywhere . Try turning heat down but then i get mounds where it isn't hot enough . Need advice . Thanks

Something else I try to do when I can access both sides of the project, that really helps with pin holes as well as other things... I weld both sides. There is a guy on Youtube whose videos have been invaluable for me for fab work in general... his page is called Fitzees Fabrication.. take a look it may be a blessing to you.

Mark Barnes · Jul 11, 2020

Jhn824 said:
Something else I try to do when I can access both sides of the project, that really helps with pin holes as well as other things... I weld both sides. There is a guy on Youtube whose videos have been invaluable for me for fab work in general... his page is called Fitzees Fabrication.. take a look it may be a blessing to you.

Fitzee is an excellent resource. He's been doing sheet metal work for ovr 30 years. Here's a link to his welding setup-

Moparfiend · Jul 27, 2020

Mark Barnes said:
Fitzee is an excellent resource. He's been doing sheet metal work for ovr 30 years. Here's a link to his welding setup-

I agree Fitzee is really good. One thing I did not see mentioned if you have blow by is to offset the angle and not go in at 90 degrees.

Welding holes

c.moo

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khryslerkid

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Bad B-rad

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Bad B-rad

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hoover

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c.moo

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Demonic

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moparlore

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eldubb440

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Bad B-rad

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Builderguy

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Jhn824

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c.moo

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747mopar

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Bad B-rad

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Jhn824

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Jhn824

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Mark Barnes

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Moparfiend

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