Best Way To Mig 18ga. SHEET METAL TOGETHER

[SCHOONER]

Hi Guys

I'm brand new to mig welding and haven't even strok an ark YET~so here I go

Lets say I wanted to mig weld a patch panel to my lower fender. Which I'm going to have to do, plus other mig welding in and around my car.

The patch is cut to fit perfectly (or at least that's what I'll be trying for).

Now I'm going to spot weld here and there on the patch piece. I'll be making sure not to warp the metal.

Now the patch piece 18ga. sheet metal is in place.

THE QUESTIONS PLEASE

How would you guys mig weld the patch piece so that it would come out really smooth. And I wouldn't have to use too much BONDO in the finishing.

Just take me thru this process please a step at a time.
Example: Make sure the sheet metal is nice and clear and then spray anti-spatter on the piece YES/NO
How far down or how would I grind the weld down. I believe it should be down to the original metal ? YES/NO
What do I look out for to ensure NO HORRIBLE MISTAKES ?

I've heard BUTT welding the pieces is best.

But you tell me I'm not telling you guys. I'M THE NEWIE

That's what I'm talking about guys. One baby step at a time so that I can copy what you guys recomemend when I'm ready to do my mig welding restoration on my car.

O.K. guys I'm in your hands, I'm all strapped in and ready . . . lol
FIRE AWAY !
Thanks guys
GOD BLESS

Schooner

 

[Justme]

Make sure the patch is a loose fit (poss 1mm all round) in the hole so the weld can easily penertrate. You will then have less to grind of & can grind it far smoother without fear of it weakening.


Justme

 

[SCHOONER]

Hey Justme

Thank you for your imput I certainly will follow you advise.
I bought these little clamps that leave a small gap between the two pieces of sheet metal when I'm going to mig 'em.
This way I'm have complete penertation through-out the mig welding process.

THANKS AGAIN GUY
GOD BLESS

Schooner

 

[Justme]

Yeh those clamps are the biss. Or you can weld little tags on to hold it in place & level.

Justme

 

[Alex]

Dont have a gap you will just blow semi-circles on the edges like undercutting.

Butt them right up together tightly and weld, if its long let it cool between runs or tack every few inches before running beads.

 

[SCHOONER]

thank You Alex

 

[Cappy]

Hmmmm, did read somewhere on here about someone who flattened a piece of copper pipe and put it behind the weld position to act as a backing plate.

I suppose part of it acts as a heat sink and takes the heat away, reducing the risk of blowing through, supporting the weld and finally stopping the gas shield from disappearing through the gap, as has happened to me a couple of times.

 

[SCHOONER]

Hmmmm, did read somewhere on here about someone who flattened a piece of copper pipe and put it behind the weld position to act as a backing plate.

I suppose part of it acts as a heat sink and takes the heat away, reducing the risk of blowing through, supporting the weld and finally stopping the gas shield from disappearing through the gap, as has happened to me a couple of times.

Hey Cappy

I read that too somewhere. I haven't started mig welding yet but what I did due to the fact I just couldn't find a FLAT piece of copper.

Solution: I went to good ol' HOMEDEPOT and bought a copper coupling.
I proceeded to cut the coupling length wise and then I flattened it out.
The piece came out to be: 2 1/4 x 5 1/4 long.

Now I have a copper flat back-up plate to place in back of my welding.
If you want a bigger piece buy some copper pipe, cut it and flatten it out like I did and you're ready to go.

Hope that helps guy

Take care & GOD BLESS

Schooner

 

[Alex]

Sounds like it may work in an attempt to stop blow through on thin metal when leaving a gap, thing is thin metal wont be much trouble for most if not all welders (not including SIP) when butted up. They will have the power to penetrate through anyway without the gap.

 

[Drains]

You can also leave the patch oversize and offset the edge of the parent material with a joggling tool. The patch sits in this offset, so the whole thing remains level. Then weld. You can then grind off all the excess weld leaving a flat surface, without losing weld strength.

If I were filling as suggested in earlier posts, I would allow a small gap in 18g (as suggested by Justme). If you dont you may find the edges warp more than they otherwise would. It is good practise to leave a root gap.

The shrinking effect of the cooling weld tends to draw the edges together, especially if you don't attain full penetration. A root gap gives you a much better chance of full penetration without putting in too much heat, although you may have to be more careful about your settings, and practise more, to avoid blowing through.

 

[lexi]

A piece of aluminium plate works as back up to build welds across or fill voids.
Alex

 

[Alex]

Root gap ok, I thought he was talking about a normal gap.

For 18 guage patching i'd still lap clamp firmly together and pay attention to warping by using text book procedures.

 

[SCHOONER]

You can also leave the patch oversize and offset the edge of the parent material with a joggling tool. The patch sits in this offset, so the whole thing remains level. Then weld. You can then grind off all the excess weld leaving a flat surface, without losing weld strength.

If I were filling as suggested in earlier posts, I would allow a small gap in 18g (as suggested by Justme). If you dont you may find the edges warp more than they otherwise would. It is good practise to leave a root gap.

The shrinking effect of the cooling weld tends to draw the edges together, especially if you don't attain full penetration. A root gap gives you a much better chance of full penetration without putting in too much heat, although you may have to be more careful about your settings, and practise more, to avoid blowing through.

Hi Simondrains

I totally agree with the gap you memtion and watching out for too much heat.
However, about that; JOGGLING TOOL I don't qet it. It sounds pretty good but being a newbie I'm not sure what in the world how its used.
And that OFFSET EDGE?
Is there anyway you have pics about the above?

Thanks guys
GOD BLESS

Schooner

 

[Drains]

Also known as a joddler or panel flanger. Check out this thread

http://www.mig-welding.co.uk/forum/showthread.php?t=1350&highlight=joggler
and this one
http://www.mig-welding.co.uk/forum/showthread.php?t=662&highlight=joggler
and some excellent advice in this one!
http://www.mig-welding.co.uk/forum/showthread.php?t=600&highlight=joggler

later
Si

 

[malcolm]

I know the original question was a general one, but the mention of body filler suggests more of a visible bodywork sort of thing.

So what on earth are you welding where the visible body is 18swg? Got to be something from the '50s or something American, but haven't bothered doing a search to find out if you've mentioned it before. What is that in metric anyway - about 1.2mm?

You have the easy life with that thickness of bodywork. For non-structural body repair I'd cut a patch exactly to the size of the area you've removed, tack one edge, then press/hammer the rest to level and tack around the remaining sides. Then seam weld while leaving cooling time to prevent distortion.

Forget anti-spatter if you're running argoshield gas. For grinding take the weld back to a flat surface but don't get carried away and thin the suffounding metal. If you have good penetration the weld strength will be fine. And of course practice on scrap to get the settings right and to get neat before welding anything that needs to look nice.

 

[dannyweld]

hi, have done much of this type of repair, cut patch to proper size and tack in with mig 0.6 wire, use damp cloth to wipe over each tack to keep cool. have seen the old schoolers using lead to repair holes, lasts much longer but is an art in its self hav'nt done it myself. you cant get away from grinding with this job, give yourself plenty of shiny metal to work with, you can get special rivets to help position and pull your work from bodywork suppliers, neal

 

[londonsean69]

hi, have done much of this type of repair, cut patch to proper size and tack in with mig 0.6 wire, use damp cloth to wipe over each tack to keep cool.

Wouldn't that cool it too fast, and maybe cause cracking?

I have heard to put the damp cloth in between the tacks, so as to help cool the metal and prevent distortion. This still allows the taks to cool naturally in the air.

Just my 0.02p

 

[Rusty]

As Malcolm said above Just grind the paint and rust off the surrounding area ( cut any rust out back to good clean metal ) cut your repair panel to size having just a minimum of clearance around the section , hold in position with a magnet make sure your repair section does not stand ' proud ' of the original panel , tack into position , check the repair section hasn't moved out of line with the original ( adjust with hammer and dolly if necessary ) then weld between tacks on opposite sides to reduce warping , when cooled grind welds back surrounding level using a coarse grinding disc ,
finally make sure the repair section is not proud of the surrounding fender then a skim of flexible body filler ( this will grip well into the grinding marks )
sand filler back to perfect finish ( keep in mind regarding imperfections in filler work ' if you can feel it you WILL see it ! ' when perfect paint finish as required.

 

[banditgsfr]

Hello mate my advise to you is that cappy as the best idea, by placing copper beneath the work piece allows penetration but also stops blowing holes in your work piece especially on thin sheet metal, and also leave a small gap as advised by some one else on here, and I also advise you not to do long runs of beads as this will lead to distortion in the panel, as you have not done MIG before, i would advise you to spot weld the piece in place, and continue to spot weld the entire piece until fully welded in to place, this will also stop any distortion.

 

[Zagan]

Hi Guys

I'm brand new to mig welding and haven't even strok an ark YET~so here I go

Lets say I wanted to mig weld a patch panel to my lower fender. Which I'm going to have to do, plus other mig welding in and around my car.

The patch is cut to fit perfectly (or at least that's what I'll be trying for).

Now I'm going to spot weld here and there on the patch piece. I'll be making sure not to warp the metal.

Now the patch piece 18ga. sheet metal is in place.

THE QUESTIONS PLEASE

How would you guys mig weld the patch piece so that it would come out really smooth. And I wouldn't have to use too much BONDO in the finishing.

Just take me thru this process please a step at a time.
Example: Make sure the sheet metal is nice and clear and then spray anti-spatter on the piece YES/NO
How far down or how would I grind the weld down. I believe it should be down to the original metal ? YES/NO
What do I look out for to ensure NO HORRIBLE MISTAKES ?

I've heard BUTT welding the pieces is best.

But you tell me I'm not telling you guys. I'M THE NEWIE

That's what I'm talking about guys. One baby step at a time so that I can copy what you guys recomemend when I'm ready to do my mig welding restoration on my car.

O.K. guys I'm in your hands, I'm all strapped in and ready . . . lol
FIRE AWAY !
Thanks guys
GOD BLESS

Schooner

I would do it like this.

Cut out a clean square etc

Keep cut out part shape the new sheet of metal to the same as the cut out.

Buy some/few welder magnets (this saves a hell of a lot of Fing around)

Place new sheet of steel so it fits right up next to the cut out edges the les gap the better, then use magnets to hold the new metal in place this will hold the new metal flush. (I take it you want it flush?)

Setup the welder so it doesn't blow holes on the edges don't use spot as your not over lapping the metal together.

You'd tack each corner then using a hammer on the back etc you'd push the metal (the metal will bend reguardless... you won't stop that from happening) into place as you tack from each side into the middle of the join on each side of the square.

let it all cool down

Then sitch weld the joins better yet sitching each side up going around as you go.

I would only grind the side you want seen to be flush.

Another way and you could look into this if your interested might be to lead the metal sheet into place rather than weld, well it's still welding but another form of it.

Leading would be quicker but may not hold the same as welding maybe a combo of tack/leading could be the go then you'd need to shave the lead for a clean surface.

You;d have to ask about leading at a body shop, not a pannel beater shop but the places that can produce bodies for example hot rods etc to see if leading will hold up it should.

It's normally used for closeing up gaps and holes in pannels, leading is much like bondo but the orginal form of it that is back from the 1800's/early 1900's.