Aircraft TIG welding

I didn?t know there was so much interest in Aircraft TIG welding hear on VAF tell I was trying to learn how to insert a photo in the forums and inserted a couple of weld photos in the test section, I got the help I needed for inserting photos but much to me surprise the photos of the welds drew a lot of attention and some questions.

1. We use W-20 size water cooled torches.
2. Lindy/Heliarc and Lincoln welders, however I have never used a TIG welder that didn?t work well so most anything out there should be pretty good.
3. Very important, we use a gas lens in the torch in place of a gas tip, the lens is a stack of very fine mesh screens that the gas (pure argon) is dispersed through and gives superior shielding over a gas tip. We test every lens we use buy attempting to weld with the electrode sticking out 3/4? past the end of the cup, if the lens fails this test it goes back or in the trash, many fail when new and others work for years and suddenly fail.
4. We use Esab-65 filler rod in 1/16? and 3/32? diameter, we have tried others with mixed results, Lincoln has an equivalent that is a close second to the Esab.
5. We use 1/16? 2% Thoriated tungsten, I am soon going to try some 2% Lanthanated as a substitute, we?ll see how that goes.

We run our torch cables/hoses over head to keep the floor clear and to protect the cables/hoses


We keep the welding machines on the back side of the wall in the back shop so we don't have to listen to them running all day.


Some more weld photos.

Welding

Beautiful work. Very high quality.

Any reading or classes (pacific northwest?) that you would recommend for those of us contemplating building (or restoring) a tube and fabric airplane?

Alschief said:

Beautiful work. Very high quality.

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Thanks AL!

jbagley said:

Any reading or classes (pacific northwest?) that you would recommend for those of us contemplating building (or restoring) a tube and fabric airplane?

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Honestly I don't know, I have hired several people over the years that had gone through the course at Clark College, they had good attitudes but I had to teach them to weld.

Russ,

Could you give your opinion on TIG vs MIG. In looking at the web site of some LSA makers it seems most are using MIG and their welds don't look anything like yours. Thanks.

billdianne said:

Russ,

Could you give your opinion on TIG vs MIG. In looking at the web site of some LSA makers it seems most are using MIG and their welds don't look anything like yours. Thanks.

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TIG is superior to MIG and is the accepted electric method for aviation. MIG is what I call fast and dirty and better suited for other things, with that said Kit Fox and others seem to be doing fine with MIG welded structures.

I have always found aircraft welding very interesting. Something I always have wanted to learn

How do you stress relieve welds that has been done with TIG ? Or is it not considered necessary in the same way as if it was welded with Oxy Acetylene ?

Jan

JanRV6UK said:

I have always found aircraft welding very interesting. Something I always have wanted to learn

How do you stress relieve welds that has been done with TIG ? Or is it not considered necessary in the same way as if it was welded with Oxy Acetylene ?

Jan

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Hi Jan,
I think your eluding to the fact that Oxy Acetylene welded structures are already stress relived simply buy the nature of the process That process gets everything surrounding the weld red hot,,, not so when TIG welding the same joint.

I’m not an engineer and can’t comment on whether these structures would benefit from stress reliving or not, however none of the parts we build for Van’s call for any further stress reliving of heat treating of any kind so there engineers must see little or no benefit in doing it, at least not on the items we build for them.

I know one manufacturer uses a mig weld to tack the fuselages together but finishes all the welding with tig.
I have done mold repair using tig for over 30 years and your welds really look great.

When welding tool steel like I do you heat the part to 800 deg F. Before welding and post heat to the same temp after welding to stop stress cracks. I also peen each weld pass to relieve stress while welding. Personally on a 4140 tube fuselage I would use a torch to heat each weld to a very dark red after each weld just to make myself feel better. Having said that, I did some test pieces of tubing and tried to break the welds. I destroyed the tubing before the welds broke and I didn't stress relieve anything.

rv9aviator said:

I know one manufacturer uses a mig weld to tack the fuselages together but finishes all the welding with tig.
I have done mold repair using tig for over 30 years and your welds really look great.

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Thanks Jim!

Tacking with MIG is ok in my book, tacking with TIG to often takes three hands Even with that said I don't do much of it.

rv9aviator said:

When welding tool steel like I do you heat the part to 800 deg F. Before welding and post heat to the same temp after welding to stop stress cracks. I also peen each weld pass to relieve stress while welding. Personally on a 4140 tube fuselage I would use a torch to heat each weld to a very dark red after each weld just to make myself feel better. Having said that, I did some test pieces of tubing and tried to break the welds. I destroyed the tubing before the welds broke and I didn't stress relieve anything.

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Cool, I've never welded any tool steel.

I think one reason stress relieving welds on a cluster is not so important is that the material is reheated several times because of the number of welds but I'm no engineer either. I've never driven a train in my life.

Stress Relieving

This is a subject that is guaranteed to start a war of words. Years ago I had a discussion of this with the then manager of what is now Aviat.(Pitts and Husky) He told me that the factory procedures called for stress relieving the engine mount but they had never done it. Nothing stess relieved, a few failures over the years, probably fewer than if the structures were oxy/acy welded.
Richard Finch in his book on welding is adament that any attempt to stress relieve with an oxy/acy torch will only compromise the structure. The process simply cannot be controlled except in a heat treat oven.
American Champion MIG welds all steel structure.

American Champion MIG welds all steel structure.

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As does Maule. However, let's note the equipment is not much like the typical cheap home MIG, and the welders are pros.

Russ,
Any paticular brand or style of gas lens you like for those tight V-joints?

DanH said:

Russ,
Any paticular brand or style of gas lens you like for those tight V-joints?

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It used to be all Weld Craft, but the welding stores like Airgas seem to have gone on the cheap and would have to special order in the real thing, they carry Radnor now, at first most of them failed my test, I have taken complete bags back for exchange on several occasions, they seem mostly fine these days.

Hear is a link http://www.weldcraft.com/2008/01/gas-lens-basics-for-tig/

I remember when Husky could not get their compasses to swing because the airframe was all juiced up from the MIG welding. It was solved by using a bulk tape eraser on all the tubing.

Husky

No MIG welding on the Husky only TIG. I don't like the MIG, just pointing out some manufacturers use it.

jrs14855 said:

This is a subject that is guaranteed to start a war of words. Years ago I had a discussion of this with the then manager of what is now Aviat.(Pitts and Husky) He told me that the factory procedures called for stress relieving the engine mount but they had never done it. Nothing stess relieved, a few failures over the years, probably fewer than if the structures were oxy/acy welded.
Richard Finch in his book on welding is adament that any attempt to stress relieve with an oxy/acy torch will only compromise the structure. The process simply cannot be controlled except in a heat treat oven.
American Champion MIG welds all steel structure.

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I always used a big propane torch to do pre, post and normalizing (stress releiving). You get a much wider, more even flame than with oxy. I'm talking about the big wand ones they sell at tractor supply for melting ice if railroads or whatever...

No MIG welding on the Husky only TIG. I don't like the MIG, just pointing out some manufacturers use it.

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They must have switched then because 15 years ago it was one of their test pilots who loaned me the tape eraser and told me about the problem.

Husky

I have been involved with the Pitts aircraft since 1975. ALL of the Afton built Pitts airplanes are TIG welded. Sport Aviation article years ago stated the Husky was also TIG. No switch always TIG.

JR, cool then. Where was the magnetization in the fuse coming from then? Anyone ever figure it out?

TIG

GTIG produces really bad magnetism. Most Pitts compasses don't work very well because of this. I have demagnetized a Pitts fuselage with a bulk tape eraser but it burned up the eraser just as I was finishing. Sacramento Sky Ranch used to have a more capable demagnetizer that they would rent out.
I have heard of demagnetizers big enough to drive a Gulfstream through.