The Stovebolt Site Forums The Shop Area Paint and Body Shop Thin metal welding frustration

I had a frustrating day today trying to weld in a patch panel in the footwell side panel. Metal is so thin there I kept blowing holes. Just had to quit for the evening

What do you do when the metal is so thin?

Get shorter on the trigger. If if still blows holes work it back to good metal and then close the hole.

Cut that thin stuff back till you get to solid metal. It's not worth chasing the holes all over the place.
Once you get to solid metal, use quick blips on the trigger. Even with good metal, you don't want to run beads like you would when welding 1/4 inch or thicker steel. Check the sticky thread up at the top of the forum on MIG welding sheet metal.

Thanks guys. I think now I got it solid. It's just going to be paper thin in places

I second that you’re on some sort of residual, thin, rusty spot. They are a pain to stop blow through.

If accessible, a copper backup plate will work wonders for you. I have a chunk of 1” copper pipe that I’ve cut up in various ways. I’ve used it in its original circle 2-3” long, uncurled sections, created little square L shapes, wrapped a flat piece over a dolly, and even put some over a piece of flat bar. The heavy metal acts as heat sink for the weld, the copper prevents sticking, and overall greatly reduces blow through and it also creates a nice flat backed weld that is easier to planish if need be.

They are handy.

Thank you Fox. Yeah I learned about that trick and have a flattened piece of pipe. I wish I could get it behind that thin metal but not possible.

Sometimes it's going to be necessary to put a scab patch over the thin spot and metal-finish the bulge that's created by the thicker area. A little metal finishing and a thin layer of Bondo can hide a multitude of cobble work. The nice thing about sheet metal work is "If it looks good, it IS good!"
Jerry

Get an oxy-acetylene rig and learn to braze or scab patch as Jerry says and use a silver-bearing solder like Stay-Brite. It will be as strong as goat's breath and the joined part will never rust.

The trouble with solder is that the metal has to be CLEAN for it to stick. Brazing alloys are a little more forgiving, as they usually require the base metal to be dull red, which usually means the rust is burnt off.

After looking at it again today I'm taking your advice Kevin. I'm going to order a new patch panel and patch a larger area in order to get to thick(er) metal. I don't want to leave it like it is. Not happy with it.

Thanks

None of this is really aimed at you Kevin WarEagle or anyone's abilities, just some general thoughts to consider about thin metal. I struggle with it all the time. Getting a little better at it.

Cut a bunch of slits (use a .040 or .060 disc) in the old patch panel and weld them up for practice and experimentation. It is hard to get the knack. Change settings and write them all down, try various angles and stick outs. That is the ONLY way to learn thin welding. To learn your machine and what methods work for you. Sometimes hot and quicker works, sometimes slower and not so hot. Sometimes you have to use a long stick out, sometimes a short is better that day. Mix it up during practice. Change duration of the trigger till you develop a method. Weld while you can reach the knobs with one hand while practicing on the slits. Turn the settings while welding to learn/see/hear what happens. Only use stacked dot welds 1-3 seconds. Slide the torch a tiny bit, down the gap, across the gap, whatever seems to work. Sometimes starting on the gap and moving to the last dot works because as the "puddle" gets hotter it then gets to the thicker spot. Other times it's the opposite. Starting at edge of previous spot works better. There are human factors involved here that can't be specified.

I hope you are using MIG with gas. Everything else is no good for thin. Some use .024, I use .030.
I do use copper and brass backer sometimes.

Mig is pretty easy to learn, but not thin metal. All metal has to be new or like new. You take .041 thick 19 ga and it has pits or wear or thinned by rust, you got .025 thick. NO GOOD. You take .047 18 ga with problems, you got .030 or less. Now factor in that those gauges have a +/- .004 thickness tolerance. This applies to the original USA metal on the truck. The Chinese patch panel tolerance is unknown. Anyway the key is practice and experimentation. An old dented, no good fender or hood makes a great practice piece. Of course you always want to use a practice piece with the same gauge as the task at hand.

You MUST clean the area near the weld down to bare metal without taking away any metal. BOTH sides if possible. MIG DOES NOT TOLERATE contamination. I also try to trim the wire stick out as much I can. Don't keep welding without clipping a ball end/burned end. You are doing quick spots, you need a super quick start and stop arc. You don't need to trim stick out when plug, stitch, seam or weave welding.

You must also clean a ground spot somewhere for the clamp, down to bare metal. BOTH SIDES for the clamp. If you can only clean one side, place clamp jaw that has the cable on that side.

Once you find the correct machine settings and torch methods, don't expect it to work exactly the same the next time. But it will be fairly close and you will be better at it.

1. Weather can change
2. Extension cords cause voltage drop
3. Output from your electrical outlet can change (utility company's fault)
4. Dirty/worn contact tips
5. Different thickness metal
6. Too much coffee
7. Not enough coffee

As everyone knows you have to have air ready at hand to cool almost each spot dot. Why not? You have all day to weld, all week, all month. if you warp it because you are lazy/in a hurry, you will have your worst nightmare. Possibly unfixable. Remember that.
Lotta stuff here, but once it's a habit, it can create more success.

Bartamos' advice is good.

Practice makes perfect.

If you aren't able to get a copper backer behind your work, don't use one for practice, as it is a completely different animal.

Soon you'll be advising other Bolters on how to weld sheet metal.

Big edit just now, but I'm done

Great advice “bartamos”!

Yes of course that's true, but welding any dirty metal is not advisable, either. For what it may or may not be worth, I worked as a commercial welder...but that was over 50 years ago when (thankfully) welding was taught more bottom-up than it is today. I also at that time had certifications including underwater and 6 hours of advanced university classes in the subject. I've mentioned silver bearing solder and a flange edge vise grip here many times. It is the fastest and easiest way I've ever found to install straight seam patch panels with minimal heat, no warping, no burn-through and the ability to re-position almost infinitely if needed. If I had any of that work needing to be done and a video camera I'd show the forum what I mean. Stay-Brite works at 430 F and has a shear strength of something like 10,000 psi. You can install patch panels using a MAPP torch if you want, but I enjoy the speed and more localized heat of an O-A rig. Plus if any solder gets outside of the seam you can dress it down easily. HVAC boys and commercial plumbers know all about the product and use it all the time, but for some reason I think most people have never heard of it.

Appreciate the thoughts Bartamos & Kevin. I thought I was just doing something completely wrong but glad to hear that the thin metal can cause problems for anyone.

I will save this thread for reference purposes.

Here are a couple of thoughts of an amateur:

1) I have always strived to just cut out the bare minimum from the rusted area, with the goal of "preserving" more original truck, but now I'm thinking to use more or all of the patch panel to get as far away from rust and into solid metal as possible.

2) Try to avoid welding across a fold or bend. This caused problems in the side footwell I was working on. So with my new patch panel the joint will be above the folds or bends in the "flat". I found that the metal in the bend is super thin and I burned thru no matter what. Also when grinding, it is hard not to make the bend thinner than the flat places.

Thanks again for the advice.

Your thinking process and efforts are spot on. With thin metal, careful grinding is as important as careful welding. Many times I weld both sides of a butt joint. I don't grind the unseen side (maybe just grind the tips/ridges down). I tack the seen side, then weld the unseen, then finish the seen side. Then grind the seen with a die grinder. Lowering it's RPM's as I get down near flat.

If you are grinding/sanding with a die grinder, and your sheet metal starts to change color or "blue", you've gotten that area really thin! Stop working the area and move somewhere else. Plus, you can feel it by pressing on it.

I have been doing all of my grinding with an angle grinder and 120 flap disk.

Is the die grinder significantly better?

For sheet metal, it is my go-to. I find I have more finesse with it. Especially with 3M purple discs. I'll rarely go to a grit more aggressive than 80.

Yes! WAY better for thin metal butt weld grinding. Better control. Light weight air tool. Small radius disc allows for grinding ONLY on the welds, NOT on the sheet metal!!!! I'm tensing up just thinking about using a 4 1/2" angle grinder. Yipes!

Use the die grinder in such a way as to have it's shaft parallel and inline with weld seam. Tangent grinding on the welds with a little 45 deg cross grinding mixed in.

https://www.homedepot.com/p/Husky-R...ut-Off-Tools-5-Pack-HDA10600AV/100081323

https://www.harborfreight.com/air-angle-die-grinder-32046.html

I'll have one in the next day or two. What coarseness of disk is recommended?

Never mind. Looks like the Home Depot disks are 75. So I guess 75-80 as previously mentioned. I have been using 120 flap disc

I use the "cut off" disc I linked, They are not specified by grit or coarse, etc. You are talking something different.

I've used a 3" electric cutoff tool with a cutoff disk (like what bartamos linked.) That's what Robert McCartney (MPandC) recommended. A flap disk should only be used for final dressing of a weld, even if then. It will be much harder to keep from hitting the base metal alongside the weld and thinning it.

A die grinder with a burr on it works well in tight corners.

I've been welding since I was 11 years old in 1948. The best advice I see here is trigger speed. I f you have a mig with spot weld function take the time to set it up for the material your welding. May take a full hour to tune it in just right. Pics of a floor pan patch and overhead weld on 57 Chevy rear shock mount plate. Done with .023 wire and heat set HIGH to blend in spots.

Patch over factory shifter hole:
[img]https://i.postimg.cc/MM8kyW3G/Int-and-57-floor-001.jpg[/img]

Overhead welds on 57 Chevy rear shock mount repair:
[img]https://i.postimg.cc/tsHhQwcx/Int-and-57-floor-002.jpg[/img]

Evan, Impressive, to me skill by craftsman is art
(I’ll step back from my welder now)

Chuck

As you pull the trigger, say STOVEBOLT and let off.

I just listen for a "zot" sound. Definitely no "bzzzzzzzzzzzzzz" sound.

Everyone thinks they are the fastest gun till the really fast gun shows up. My friend and I were making a sugar beet alcohol still at Glitch Industries in Dallas when we needed a stainless 1/8npt to 1/4 inverted flare fitting welded into a panel. I carried it over to a guy welding up stainless ceiling joists for a sulphur mine in Mexico that had 6x6x1/2" thick angle irons for flanges. He sat my 1/8 " pipe fitting on his table and made an almost instant pass around it WITHOUT re-setting the heat. When I remarked about this he said "Oh, you weld?" I just looked at him and said "I USED to."

For selecting your cut off wheels for grinding welds, the cheap ones I think you’ll find going up in a cloud of brown dust in the air. I go to my local welding supply and get 3” x 1/16” wheels that are rated for stainless steel. Costs more, sure. Lasts about 4 times or so longer than the HF ones. Very little brown dust in the air. Grinding process using the cutoff wheel:

www.youtube.com/watch?v=V2WHT_zMOE8