MIG Brazing for Patch Panels

[e3pres]

I'm in the middle of some serious metal work on a 1958 Pontiac that I'm restoring. To be completely honest, I'm not much of a sheet metal welder. The MIG welds wind up very hard and I end up grinding too much and thinning out the surrounding metal. Long story short: I'm not very good at this, but my budget doesn't allow just turning the project over to a fabricator at the moment.

That said, I've recently been reading about MIG Brazing using silicon bronze and 100% argon. This seems like it might be a better option for me since it puts less heat into the metal and is supposed to leave a softer joint for grinding. Does anyone have any experience with this technique?


Thanks,

Adam

 

[rustyjames]

The only problem with that is most of the plastic fillers that I know of don't seem to stick that well to bronze.

 

[Professur]

Head to the local bone yard and buy a scrap fender and practice. Get better at setting your gaps, and get better at welding. For metal as heavy as you've got there, you shouldn't have any difficulty if you've set your welder up right. Do you really want to treat a '58 that badly? I use straight CO2 with .023 wire and never have any worries. Are you trying to draw a bead, or are you hopping about?

 

[rsanter]

Copper back the joint you are welding.
The MIG weld does not stick to the copper.
I suspect you are not getting good penetration for fear of burning through so you are getting too much/too tall of a weld bead.
The copper will also help to pull out excess heat that contributed to the blow through and warping
Don't over grind the weld area. Knock 80-90% of the top of the weld off then switch to a sanding disc

Bob

 

[Showkey]

There is "easy grind mig" wire specially wire for body work.
Mig is so much better for avoid heat distortion and flush welds.

As mentioned "bead height", grinding and sanding all are skills that take technique and practice.

http://www.esabna.com/us/en/products/index.cfm?fuseaction=home.product&productCode=9492

 

[astroracer]

Actually, when welding patches into a body you should be tack welding them in, not pulling beads...
Tack the patches in and take your time. Let the tacks cool to room temp and work your way slowly around the patch until it is all welded in. Working slowly and keeping the heat affected zones to a minimum reduces warpage in the body panel. This also reduces the required grinding and thinning of the adjacent steel.
Mark

 

[countryroad82]

Here is a short vid I made of welding in patch panels awhile back. Need to quit being lazy and update the channel lol.

This should give you an idea on what the welds should look like. Nothing is easy about this **** when you're starting out. You get better with experience!

 

[Capt Chrysler]

Ez grind and small grinding discs

Capt. Chrysler

 

[Fender1325]

Im redoing a 50 cadillac myself - mainly floors right now so its easy to botch a little here and there. Its all 18 gauge.

Lets make sure youre not setting the machine too cold first. It should sizzle like bacon "ssss". Turn your wire feed down until you get a bland kind of "ffffff" sound, and an inconsistent arc.....(seems crazy I know).....then turn it up until it sizzles like bacon. If you go too high you'll get more spatter - thats molten metal not transfering because theres not enough heat - dial it back until you get a regular sizzle and a consistent arc.

Take a piece of scrap and experiment. You'd be surprised how hot you can have it because youre only squeezing the trigger for one second.

From there move around the panel only putting 1 second tacks, dont pull the gun at all just squeeze it and stay put for 1 second or less. Jump around until its all overlapped with tacks.

Ive seen guys online use cutting or grinding discs to dress the weld rather than a flap disc. This cuts only into the weld surface rather than touching the surrounding metal.

Setting your gaps in your patch is helpful too to reduce the weld from sitting on top rather than lower in the joint. Practice with scrap off the car and experiment with gaps.

 

[kkroger]

Easy Grind Wire, Tack, GRind your Tacks, tack some more, Grind your tacks... you can string but not more than about 3/4" at a time and hop around... always let cool and grind your welds as you go... I had a cutlass that someone before I had it had brazed in some metal, and it was the first place it rusted out... all along the seam. When I ground the finish back to take a look I found brass.... not good...

 

[e3pres]

Thanks, guys. It sounds like the easy grind may be the way to go. I'll order some and see how it works. I'm getting better at actually making the tacks. Better fit up is helping. I can't wait for this part of the project to be behind me!

 

[Showkey]

I can't wait for this part of the project to be behind me!

You know your close to the end..... It is just about the time your get really good at sheet metal MIG..........flat welds, perfect penetration and just a little grind

 

[Professur]

This is why you practice on a scrap fender .. not on your 60 year old classic.

 

[bgarrett]

do not put brass on car body. the next guy will have to cut it out and do it right

 

[BLACK DEATH]

Ok what's better to mig with, a 110 or 220 machine on thin metal like 18 or even 22 gauge panels? Seems my 220 can't do 22 metal with 23 wire worth a dam

 

[Showkey]

^^^^^^^its all about the machine setup and technique.........I use 240v 180 amp MIG for all sheet metal repairs. 120 volt machine can be a little more forgiving. Any Flux core machine on sheet metal is not the best.

There are many variables like kind of new metal and condition of the old metal, paint and rust cause all sorts of problems.

 

[countryroad82]

Ok what's better to mig with, a 110 or 220 machine on thin metal like 18 or even 22 gauge panels? Seems my 220 can't do 22 metal with 23 wire worth a dam

^^^^^^^its all about the machine setup and technique.........I use 240v 180 amp MIG for all sheet metal repairs. 120 volt machine can be a little more forgiving. Any Flux core machine on sheet metal is not the best.

There are many variables like kind of new metal and condition of the old metal, paint and rust cause all sorts of problems.

Machine setup is the key to welding thin metal. I prefer a 220 welder as I feel I have made some of the purtiest tacks, let me reiterate TACKS, with a larger machine. They are a little more versitile as to what you can weld i.e. 220vt can go a lot larger metals, so one machine does it all. I own a little ol' 110 Hobart 135. I learned how to weld with larger machines, it took me a little while to get used to the 135, but now after owning the thing almost 20 years I can lay a nice bead with it and it is all I use to weld in patch panels.
As Showkey said, flux ***** and also make sure to clean the area well. Bare metal is the best. I'm just as guilty of leaving paint on 'a small patch' due to shear laziness and I pay for it! Makes some of the gawdawfulest welds that I get to clean up, just don't do it. The metal condition also plays in part, if it is weak from rust it really needs replaced, otherwise you just keep blowing holes through it. Last but not least when welding sheet metal, you're not going to be able to run a full bead, all you can do is multiple tacks or stitches until you get the entire panel welded up. Also jump around from one end to the other and allow it to cool or you get to chase around a dent you caused from overheating the panel causing it to warp. If you have any other questions please feel free to ask and somebody will help you out or shoot me a pm. But all in all it just takes practice to get good at it.

 

[BLACK DEATH]

I'll give that a try n practice on a few pieces first

 

[VoodooCLD]

Are you using flap discs to grind down the welds? If not, you should try them. I find them much more forgiving when grinding down body weld seams.

 

[SteveH-CO]

...simply....must....reference....this....thread: http://www.garagejournal.com/forum/showthread.php?t=182565

Even if only read the first page, it's invaluable. Using slicing disks to grind the welds was something I learned here, and it's easier to control the grinding, doing that.

 

[dffay]

I've been welding for years. So I have a fair amount of confidence in my ability to do, or not do certain projects. I'm going to be filling gaping holes in the firewall of my '53 Ford F-100. To make life easy I will be welding the patch panel circles from the inside of the cab. With 100 percent penetration, I won't have much grinding on the visible engine side. Having done it before, I've seen it work. I use a series of short welds if not long tacks, and skip around so I don't lay in more heat than the panel can deal with. The inside of the cab, though it will be finished with noise coating, and such doesn't have much raised weld either. Just go slowly, skip around, and have just enough heat for full penetration.