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Fri Jun 06, 2014 12:20 pm

Hi ,i'm interested in trying some thin sheet metal butt welding and I have come across some techniques that vary greatly, particularly this type.

from http://www.cartechbooks.com/techtips/mig-butt-welding/

This method must involve a crazy amount of weaving which would create a unnecessary amount of extra heat. They must have bridged the gap using tack welds and then used a pattern that went slightly up the sides and then deposited weld on the edge of the part that bridged the gap. There is no way the method the author described did those welds.Am I wrong?

Fri Jun 06, 2014 5:11 pm

naw, If he had alternated one side then the other and stitched it together then it would have more texture.
It is possible to just stay in the center and pull the weld along over a gap that big. with mig, tig or gas. The key is to have the heat input and travel speed JUST RIGHT, which with mig would almost have to be a pulse technique. maybe 1 second at a time, which is why it's so funky lookin, and takes a long time.

Not much point in doing that, because you end up with a huge 1/4 diameter bead. Any time you try to weld a gap bigger than the material thickness it's a stupid idea........but we do it all the time :lol:

If your in the process of doing this type of stuff and have a good transformer type machine, try dialing back the wire speed until you are getting into globular transfer. this is when you pull the trigger and instead of bacon popping you get a hiss and a glob is forming on the end of the wire.....not touching the work. The glob will tend to fall onto the work in a regular interval. Soon as that glob falls let off and wait 1 or 2 seconds and do it again. If you can time it right you can pulse 1 or 2 seconds at a time and have one or two globs fall.
It is not always the right technique, but if welding metal thinner than your welding wire then turning turning the wire speed down to semi-globular may be the way to go!
Not using .023 wire? well then better get some or try this :wink:

To keep the gap the correct you can fit it best you can without being too small, then tack in place, maybe even overlapped in some areas. Then use a thin cutoff wheel, or blade, to slice through there and MAKE the gap the right size :wink: Don't need any dimes.

Sat Jun 07, 2014 6:53 am

I think just the right amount of beer would help too. :lol: The beast Ice specifically if I still drank.

So do I start the puddle in the center of the gap? :? Thanks for the lengthy explanation by the way!

Mon Jun 09, 2014 9:53 am

theKbStockpiler wrote:
So do I start the puddle in the center of the gap? :? Thanks for the lengthy explanation by the way!

^ That gap was HUGE

i find it easier to have a small gap, turn the heat/wire speed down and pull the bead from one side of the gap to the other (if you can't zip it with a spot weld).

be sure to keep things cool too

Mon Jun 09, 2014 6:54 pm

I have to fill a lot of holes soon so this subject is going to get a lot of attention at the perfect time. I was very surprised that the edges of the pieces I did ,did not just melt off like when you have clamps too far a part and one piece warps away from the other and the closest piece to the arc melts off. Interestingly the edges only melt off when you try to move the puddle but not if you just let the puddle spread out. So actually burnthough is only an issue if you are moving the gun nozzle.

I have a bunch of metal strips prepared to test on so I'll do those this week. I'm going to try to lay a short stitch bead instead of a tack/puddle weld. I want to get a paradigm that will also work with 'out of position welding' like horizontal. I'll try pulling the pool across the gap ,see if a slight zigzag will work a short distance and see if nozzle angle (push/drag) seems to make a difference.

Tue Jun 10, 2014 9:41 am

these clamps make it super easy to butt weld:

Tue Jun 10, 2014 11:04 pm

To bridge the gap at first well yea you have to go across!
but after that it's just a matter of welding....... to the weld, and if you can get the puddle to expand JUST to the work and no farther it will pull along. But lets just do that for fun eh? I met a guy once who was a fitter. He just fit the pipes together and another guy welded it. He said he made more$$ than the welders. I believe it. But trying to weld bad fitting is a good way to "practice". yep, got lots of practice

For filling holes use a copper thingy to back up the hole if possible.
I got a copper knob on a length of 1/4 all-thread I use for trim holes. It "was" a decorative knob for a cabinet or something, but it's not so decorative anymore :lol:

Tue Jun 10, 2014 11:07 pm

theKbStockpiler wrote: Interestingly the edges only melt off when you try to move the puddle but not if you just let the puddle spread out. So actually burnthough is only an issue if you are moving the gun nozzle.

yep, exactly. That's the whole key right there. Now how to DO it.......somewhat harder

Wed Jun 11, 2014 7:12 pm

I did a few welding test pieces and these are my observations.

-The weld pictured in my original post is not a stringer/stitch bead.

-If you have a gap that is the thickness of the sheet metal , you can not do a stringer/stitch bead. It will burn through the edges and if you move fast enough not to do this ,a weld puddle will not develope. This gap distance is set before tack welding the pieces together.

-If you space the pieces the exact amount desired before welding ,the tacks will contract when cooling and noticably decrease the gap. Therefore you have to gap the pieces or they will buckle. :x

To fill or to stitch weld: That is the question. Any other method and you have to clamp a heavy piece of metal to the work to act as a heat sink,etcetera.

It looks like you want just enough of a gap so the panels don't buckle against eachother after the welds cool which is a little less than Edit a third of the thickness of the work.Otherwise you basically have to do a series of tackwelds to prevent burnthrough. If your gap is too big you have to do a series of tackwelds and basically fill the gap incidently joining the two separate pieces.

Wed Jun 11, 2014 8:11 pm

How thin is this sheetmetal?

I just tried a .080 gap in .020 sheet, using .030 wire and CO2, it worked. :lol:

Thu Jun 12, 2014 6:51 am

19 gage: I have variable voltage control, can set it so low that the wire stubs into the work piece ,then arcs ,back and forth , but that is really the same as a series of tack welds. I have two strips of sheet metal tacked together about 1 1/4 inch a part and trying to start an arc in between the tacks. It will work momentarily but it is not sustainable. I'll do a few more tests later today. :wink:

Thu Jun 12, 2014 5:50 pm

Okay I did some more test. With .023 wire and a gap that will leave maybe 1/3rd of the thinkness of the sheet metal (19gauge) after the tacks have cooled/contracted I can move the weld puddle (tack) maybe 1/16ths of an inch. Then I have to let the very short bead :almost a tack, cool until it is not red and then I can lay another 1/16th" bead plus the length of the weld puddle.

I can't get any reasonable results any other way without using some sort of (deposit metal) method as I create basically an oval bead or a tack moved about 1/16th".

If you have a large ass gap like the picture in my first post. You have to first fill in the gap and then start your weld puddle from that ,let it cool from red and then do it repeatedly which is not even a stitch weld let alone a bead.

Thu Jun 12, 2014 8:15 pm

mango-smoothie wrote: these clamps make it super easy to butt weld:

It should be noted that those clamps ONLY work where you have access to both sides of what you're welding, otherwise you need clecos.

Thu Jun 12, 2014 8:21 pm

theKbStockpiler wrote: Hi ,i'm interested in trying some thin sheet metal butt welding and I have come across some techniques that vary greatly, particularly this type.

That gap is HUGE, like 6 times wider than what it should be.

Set your gap correctly, use a LOT of sheet metal clamps to keep the panels aligned. I won't get into tacking preferences because everyone is different. Do NOT run beads ! Tack here, tack there and keep moving around while letting areas cool, take your time. Remember that grinding the weld also produces heat.

Sun Jun 15, 2014 12:38 am

theKbStockpiler wrote:

If you have a large ass gap like the picture in my first post. You have to first fill in the gap and then start your weld puddle from that ,let it cool from red and then do it repeatedly which is not even a stitch weld let alone a bead.

Yeah. Anything below 16 gauge a pulse technique is usually the way to go. Even filling big gaps in 11 gauge you won't be going more than a few seconds at a time.
by this I mean alternating about 1 second on, one second off. Or thereabouts as needed.

It's not the same as a tack, a tack is half blind and a cold start which is never very good. The first second of any mig weld is always too cold, that's one of the downsides about it, but it's easily overcome you just start in a spot that isn't important. If you start on a spot that is already glowing red then it works great.

by pulse I mean you freeze in place and wait around 1 second, the spot will be cooled a little but still glowing(800+degrees) which lets you restart the arc right where you left off. By observing the glow you can control temperature as you go. But anyhow as long as it does not cool too much it will be have complete fusion and thus is a "continuous weld" tho you are not continuously welding.

I always go up one power setting for tack welds, and even then they are brittle from being too cold. Very different thing.

think of it like this: you can always have the settings a bit too hot and stop and let it cool for a sec as you go.......but you can't do anything if the setting is too low except make poor welds. it is kinda hard to learn to freeze in place....don't move the gun at all..... need to pretend you are a robot :wink:

Mon Jun 16, 2014 5:10 pm

I had the welder out again and #?*!-ed up my car some but I learned quite a lot. :twisted:

The fill method used in the picture of my first post is not as far out as I first thought. What they did was to first fill one spot between the two pieces of sheet metal. Then they overlaped this quite a bit more so then you would do when starting a new weld to continue an old one. That is part of the reason the bead is so thick. I usually try to over lap by maybe 1/3rd of the the last weld puddle diamter, but you have to go just a little more than that maybe just under I/2. When the puddle is created and expands outward from over lapping the bridged part, it fills the gap while it is at it and also engulfs ;for lack of a better term, the sheet metals edges as far as the puddle size allows with out burn through if properly done right.

Thu Jun 19, 2014 9:58 pm

Keith wrote: mango-smoothie wrote: these clamps make it super easy to butt weld:

It should be noted that those clamps ONLY work where you have access to both sides of what you're welding, otherwise you need clecos.

You can also buy a set of those clamps at harbor freight for $8. there not as nice as the extruded aluminum one but for the money.

Casey

Fri Jun 20, 2014 3:46 pm

I intend to hit HF up for those clamps when the situation calls for them. Thanks for enlightening me on them. :D

Please excuse the redundancy:
Here's an image that exploits the factors of butt welding two thin sheets together.
https://www.flickr.com/photos/82775806@N03/14445797166/

https://www.flickr.com/photos/82775806@N03/14445841326/

It's not really butt welding. Its filling the gap between two pieces that you don't feel like fixing the right way, more like gap welding. The gap is filled and then you weld onto your fill along the seem as far as you have to while catching the edges of the two pieces as you are at it. It's a great technique but the presentation is a little misleading. Its not really all that intriguing after you have it figured out but it is a great option.