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Old 02-14-2019, 10:21 AM   #1
pimpston65
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gas welding vs mig

has anyone used gas welding with this welding for 18g panels as well as mig welding. i have very long sections to weld, and most have no access to the backside. so my issue is distortion control. so the question is, does gas welding do a better job for my application? thanks for replies...
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Old 02-14-2019, 10:30 AM   #2
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Re: gas welding vs mig

I would use a MIG 1/8" at a time and a wet rag on it fast after the stitch. Then move to a different area & repeat. May take longer but less distortion.
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Old 02-14-2019, 11:03 AM   #3
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Re: gas welding vs mig

Depending on the panel and location, I either TIG weld it with silicon bronze wire, or MIG weld it with .035, or thinner wire.
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Old 02-14-2019, 11:30 AM   #4
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Re: gas welding vs mig

I mig with .023 wire and never run a bead, spot only.
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Old 02-14-2019, 11:32 AM   #5
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Re: gas welding vs mig

I have one of those torches at work, and I've played with it a bit. It claims to cut like plasma and weld like TIG. I was not impressed; I didn't find it any different.

Gas welding body panels together might be a better way to go than MIG, because the weld is annealed in the process, which should make hammering the weld out easier.

But you also run the risk of putting too much heat into the panel and having to deal with that.

Search up gas welding bodywork videos on Youtube and see if it's your cup of tea.

I'm not very good at it, honestly. I usually MIG.
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Old 02-14-2019, 02:08 PM   #6
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Re: gas welding vs mig

I used my mig with .023 wire...using the spot method I had no real issues....
MP&C has a slick little gas welder setup...
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Old 02-14-2019, 03:12 PM   #7
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Re: gas welding vs mig

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Originally Posted by pimpston65 View Post
has anyone used gas welding with this welding for 18g panels as well as mig welding. i have very long sections to weld, and most have no access to the backside. so my issue is distortion control. so the question is, does gas welding do a better job for my application? thanks for replies...

If you can do a no-filler fusion weld, the OA or Tig does a nice job, but I think gravity helps any welding on a horizontal plane to sag a bit, looking like an undercut. Once planished, it will tend to fill in any voids that you should see a fairly flat panel, both front and back, requiring little to no filing/grinding. The caveat here is that you absolutely need access to the rear side to be able to planish.


What areas are you welding that do not have rear access?
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Old 02-14-2019, 05:43 PM   #8
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Re: gas welding vs mig

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If you can do a no-filler fusion weld, the OA or Tig does a nice job, but I think gravity helps any welding on a horizontal plane to sag a bit, looking like an undercut. Once planished, it will tend to fill in any voids that you should see a fairly flat panel, both front and back, requiring little to no filing/grinding. The caveat here is that you absolutely need access to the rear side to be able to planish.


What areas are you welding that do not have rear access?
the rear quarter on my suburban, both sides
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Old 02-14-2019, 05:45 PM   #9
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Re: gas welding vs mig

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the rear quarter on my suburban, both sides
i have my mig setup for great welding, i just wanted to try another type of welding. thank you all for the input!!!
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Old 02-14-2019, 06:45 PM   #10
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Re: gas welding vs mig

You’re likely going to need planishing no matter the weld method, to remove the distortion. We’ve used long armed, double jointed, limber guys on the inside with a dolly and another on the outside with the hammer. Some light taps will find the dolly, then a couple good raps to stretch that weld back out, move on to the next.
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Old 02-14-2019, 07:10 PM   #11
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Re: gas welding vs mig

i agree with the above mention of TIG. reason being, the filler is generally softer. what this leads to is...on a hot day, the filler will move with the panels.

i can always see a panel seam when done with GMAW or Oxy Fuel.

rarely does any DIY'er hammer finish the weld joint.
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Old 02-16-2019, 07:47 PM   #12
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Re: gas welding vs mig

have you looked in to the newer 2 part glue stuff made just for panel bonding ?

no heat / strong as a weld and the factory is using it all over the place these days .
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Old 02-16-2019, 11:44 PM   #13
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Re: gas welding vs mig

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have you looked in to the newer 2 part glue stuff made just for panel bonding ?

no heat / strong as a weld and the factory is using it all over the place these days .
i saw something about it, but never thought to use it.
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Old 02-17-2019, 12:38 AM   #14
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Re: gas welding vs mig

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have you looked in to the newer 2 part glue stuff made just for panel bonding ?

no heat / strong as a weld and the factory is using it all over the place these days .
While it is true the factories are using glues, they don't use it in putting a seam down through the middle of a visible panel, as it more than likely will result in ghost lines in your paint. The glues require a flanged seam for the two panels to overlap, two thicknesses heat up and then cool down slower than one thickness. Given enough cycles of heating and cooling, the differing expansion and contraction rates will produce a ghost line showing exactly where the seam took place, like in this tailgate repair:


https://www.youtube.com/watch?v=OGhFEfVqxb0


Pimpston, one option may be to remove the entire quarter, make the needed repairs, and then replace. Or perhaps remove the outer wheelwell to provide access for planishing the weld seam and replace the wheelwell when complete. Or use the glue and live with ghost lines. This is exactly why weld seam locations should consider the need to planish the welds. Don't always take the smaller patch is better way of thinking, plan out the entire operation. Buy the larger panel if available if it makes the install easier, which may mean access for planishing. Use two people to planish if the inside and outside are not accessible by one.
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Old 05-09-2019, 09:18 PM   #15
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Re: gas welding vs mig

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Originally Posted by MP&C View Post
While it is true the factories are using glues, they don't use it in putting a seam down through the middle of a visible panel, as it more than likely will result in ghost lines in your paint. The glues require a flanged seam for the two panels to overlap, two thicknesses heat up and then cool down slower than one thickness. Given enough cycles of heating and cooling, the differing expansion and contraction rates will produce a ghost line showing exactly where the seam took place, like in this tailgate repair:
They are using it all over now like said above. They prefer a rivet bond over plug welding now too. Rivets over the structural adhesive joint. A cold repair/hybrid joint is a great way to repair if it's hidden, and your not going for an OEM restore. Not many places on our trucks for that though. I think it's mostly a modern assembly and collision shop repair technique. But MP&C seems like a collision man so... good info from him. I am considering a small repair in my floor pan to abate some rust using structural adhesive, rivets and a flange. No heat, and I could repair right next to the fuel tank. I am considering it for that. But then again, the floor may provide some good practice for stitch welding. I just hate to remove the fuel tank and lines.


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Old 05-09-2019, 10:01 PM   #16
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Re: gas welding vs mig

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Originally Posted by pimpston65 View Post
has anyone used gas welding with this welding for 18g panels as well as mig welding.
No outer body panels are 18 gauge. More like 20. You and anyone else can get a caliper and measure.
Gas is less hot than arc, but regardless, you need to planish and on a fleet bed, you can't. You need really tight/cloe fit to do good gas welding, and actually want pretty close fit w/ mig/tig. Long ago, people would gas weld and planish while the weld was still red hot (hammer weld). This knocks down the weld and expands the weld that would be shrunk by the heat. It seams this was done with filler rod.

Last edited by franken; 05-10-2019 at 01:20 AM.
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Old 05-09-2019, 10:43 PM   #17
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Re: gas welding vs mig

pimpston65



. How is your project going?
Lot's of good idea's that was shared
in this thread you started. Thanks
I got a few idea's from this.




.
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Old 05-09-2019, 10:49 PM   #18
pimpston65
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Re: gas welding vs mig

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pimpston65



. How is your project going?
Lot's of good idea's that was shared
in this thread you started. Thanks
I got a few idea's from this.




.
its going well. im working on the complete floor pan and maybe i'll switch the firewall or patch areas of rust, at least i havent needed to much in the way of tools to get it done. finding the time is the major issue. i work alot to pay the bills and not much time for the truck, but its moving along and should have a roller soon.
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Old 05-09-2019, 11:08 PM   #19
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Re: gas welding vs mig

Great news.
Bills are first.
Then truck project is next to release the stress.
Keep us updated.
Have you started a build thread?
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Old 05-09-2019, 11:24 PM   #20
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Re: gas welding vs mig

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Originally Posted by Getter-Done View Post
Great news.
Bills are first.
Then truck project is next to release the stress.
Keep us updated.
Have you started a build thread?
so true. i have one called "finally come" should have read finally came but i rushing and cant change the name...
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Old 05-12-2019, 07:34 PM   #21
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Re: gas welding vs mig

When I first learned to do panel repair I was helping a guy build model A's. Everything was gas welded. What I was taught was gas welding and doing it stitch and hammer. Seams were all but welded a 1/2" or so at a time and hamered when hot. Move down a foot and do it again. Once done the weld was cleaned up out came the torch and a wet rag to work the seam back flat. Same thing can be done with a mig gun and .023 wire and stich welding. Then heat and shrink. It takes practice. Google shrinking disc and watch some videos.
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