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How to weld 0.025” 6061-T6 aluminum?

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How to weld 0.025” 6061-T6 aluminum?

Postby OliverR » Tue Feb 13, 2018 12:25 am


I want to weld some 0.025” 6061-T6 aluminum, on a homebuilt aircraft I am working on.

To practice, I ran beads on some scrap pieces, without a problem. Not pro level, but I felt that I was in control of what I was doing.

However, when I laid a second piece on top of it and tried to weld them together, this was virtually impossible. No matter what settings, how I held the torch or on which area I tried to focus the arc, the upper piece would melt away before the lower piece would form a puddle.
When I tried to melt some filler on the lower piece first, hoping that it would flow into the joint, this also didn’t work.

I spend quite some time practicing, watched tons of videos, read through the forums, but no success. I am now wondering, if I do something wrong with the preparation of the two pieces or if my setup is not suitable for this job.

This is what I have:
Eastwood TIG200 AC/DC welder
Blue, 2% lathaniated 1/16” electrode, ground to a sharp point, but I also tried to ball it
1/16” 4043 filler
100% argon gas
#7 gas lens

15 cfm gas flow
25 amp (I also tried more and less)
-2 clearance effect (I also tried much more and less)
0.5 second pre-flow, 5 seconds post-flow

Parts preparation:
Wipe with laquer thinner
Clean with Scotch Brite wheel or stainless steel brush
Wipe with laquer thinner again

Some of the test beads on the 0.025” sheet metal:

After the parts had cooled down, I cleaned them, turned them around and positioned them for welding:

How would you go about welding these two parts together? Do I need to change something in my equipment / process?

The other topic is, that want to add two more fittings to the fuel tank, which is also only made of 0.025” 6061-T6 aluminum.
This is what the factory installed fitting looks like:

This is the type of fitting I want to install:

A friend suggested that I should heat the fitting up with a torch and then start to weld at the tip of the red arrow, letting the filler run down to the sheet metal. What are your thought on this?
I will order a few extra fitting and practice first, at over $3 / piece, I however want to keep scrap at a minimum.

Finally, note the fine weld in the edge of the tank. It goes along the edge of the tank’s side wall and the bottom. How would you go about making such a weld?

Thanks for your help in advance!

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Re: How to weld 0.025” 6061-T6 aluminum?

Postby weldyM » Thu Feb 15, 2018 9:09 am

The only picture I'm seeing is of the fitting. An image of the specific joint you're welding would be helpful.

I wouldn't use lacquer thinner, I'd use acetone. Search 'acetone vs lacquer thinner'.

If that welder doesn't go down to somewhere around 5 amps on AC you'll have a really hard time welding something that thin.

I would also purge it.

Here is some .025" I've welded. All of it purged
800-003.jpg (31.41 KiB) Viewed 142 times
800 20140624_163137.jpg
800 20140624_163137.jpg (33.37 KiB) Viewed 142 times
800 20140716_185908.jpg
800 20140716_185908.jpg (33.5 KiB) Viewed 142 times
800-002.jpg (40.05 KiB) Viewed 142 times
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Re: How to weld 0.025” 6061-T6 aluminum?

Postby tungstendipper » Thu Feb 15, 2018 2:56 pm

The only picture I can see is the last one.
Lincoln MP 210, Lincoln Square Wave 200,
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Re: How to weld 0.025” 6061-T6 aluminum?

Postby OliverR » Fri Feb 16, 2018 11:41 am


Thanks for letting me know.
I uploaded the pictures to my Google Photos account. I'll check the settings, if your reading the forum from work, access to Google Photos might however also be restricted.


Your welds look beautiful!
I don't want to take any chances and will therefore simply get Acetone, just to be on the safe side. I will also try to grind the tungsten at a wider angle, to get a more focused arc.
The weird thing is, that I can start a puddle just fine, add filler even to a point at which I have a good sized bubble on one piece, but am not able to make it flow to the second piece with which I want to join it. It is as if the second piece would immediately be covered in the white stuff, surrounding the original puddle and repel the added filler. When I apply more heat to the second piece, it would melt away, before forming a clear puddle.

A friend of a friend is a very experienced, semi-retired welder, who now instructs a two local colleges. He will come to our house next week, to look at what I'm doing but to also give it a try himself, with my machine. If it turns out that my machine is not suitable for this thin aluminum, I can also try his fancy $4,000 Miller TIG welder.

Welding the thin aluminium was originally only a ‘nice to have’ but now it has become a skill I want to master. ;) 8-) :lol:
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