# Which weld to use

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#### Medic9204

##### Well-Known Member
Okay, I'm about to learn how to weld but need suggestion and ideas of which method to go with.

I'm welding 4130 tubing and sheet steel for the fuselage.

What's best? gas, tig, mig, something else?

ALL opinions are welcome, and I'd appreciate reasonings.

Thanks!

#### velojym

##### Well-Known Member
I'd probably stick with gas, to keep it simple, and done right, you can normalize the welds as you go.
Some of the others, I've heard, may have advantages, but I need a little more edumacation and equipment than I can afford to do that right now.

#### wally

##### Well-Known Member
Learn to oxy-acetylene (gas) weld. It is a good and tried method of putting 4130 tubing together.

It is not hard to learn and the skill will transfer to nicely when you try to TIG weld. Similar techniques.

Wally

#### Medic9204

##### Well-Known Member
What does it mean to normalize a weld?

#### CAB

##### Well-Known Member
They tell me..........

Seems we're getting more and more "rag 'n tube" types around here. COOL! :smile:

This is a subject that comes up all the time on the Bearhawk lists; and the overwhelming consensus is: gas is best. They use phrases like thermal shock and normalizing and stress relief (thought that was fishing : ).

Someone who actually knows what they're talking about could probably explain this stuff.

CAB
Bearhawk # 862

#### Medic9204

##### Well-Known Member
Actually, my plane is half and half. The fuselage and empennage is rag and tube and the wings are aluminum. It's a good combination, I think.

It seems the consensus is gas, so far. Yeee, hah.

#### MarkP

##### Member
I've used both gas and tig on 4130. Learn to gas weld first, then switch to tig. Gas is cheaper to start with, about $500. ti start . A good tig is$1500.00 up

#### Rhino

##### Well-Known Member
Originally posted by Medic9204
...The fuselage and empennage is rag and tube and the wings are aluminum....
Bearhawk???

#### Medic9204

##### Well-Known Member
Sonerai.

How does anyone feel about arc welding? I ask because my dad has a nearly-new, VERY nice arc welder he picked up at an aution.

#### MarkP

##### Member
I have not seen much about arc welding. Mostly NOT recommended for aircraft, the weld is to brittle or something to that affect. But, I have read that one manufacture has used arc for many years, possibly Citabria. I was amazed to read that. The welders, though had to be recertified monthly.

#### Craig

##### Well-Known Member
Normalizing

When we weld a joint, we induce various stresses. It just isn't possible, for example, to weld a tube cluster all in one go - each welded tube joint starts at a centerline, goes 90 deg., then starts at another centerline, goes 90 deg., and so on. And each tube entering the cluster has a different length, probably different diameter and wall thickness.
So - the weld induces stresses in the metal. You can see this if you make a simple tee-weld, one tube at 90 deg. into another. If you will put the tbe base along a straight-edge, you'll see that it gets bowed. Not to worry.
Normalizing simply means that we are heat-relieving the stresses that we've just put in. Heat the whole joint to a very dull red for a few inches out from the welded area. Now let it cool in a draft-free location. All done.
If you get a bow in a tube from the welding, just remember that metal will travel TOWARD the heat, and give it a little. It generally straightens right out.

Of the two methods, I greatly prefer oxy-acetylene for versatility. And I like TIG for the ease of welding, accuracy, and good penetration. Each has it's adherants.
Do stay away from arc-welding and MIG welding on 4130. Very difficult with the thin walls, and sometimes (maybe it is just me) makes for brittle welds.
Check your welding rod with both O-A and TIG - use the right stuff. Any A&P can point you in the right direction to what is available in your area.

#### jumpinjan

##### Well-Known Member
I heard from a friend that one can't even use the copper plated welding rods because the copper doesn't help in making a strong weld. So I assume an unplated rod is the better approach? I haven't check at the local welder supply yet, but is his thinking correct?
So, are you guys actually saying that TIG is okay with a normalizing step after the joint is TIG'd? That was the way that I was going on my first steel tube project.

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#### wally

##### Well-Known Member
Yes, TIG makes pretty welds. And normalizing relieves the stresses in the finished joint.

Just get some plain 1/16th rod and have at it. The rod is available in 4130 material. I think some plans even recomends using a mild steel welding rod.

Arc welding is just the ticket for building the trailer to take the plane to the airport. Or a nice strudy work table.

#### cmeek

##### New Member
I originally learned to gas weld for the purpose of building my airplane. I took the EAA gas welding course and got a gas welding setup. I practiced through almost 2 full 92 cubic feet tanks of gas before I felt ready to weld on the plane. I welded a few parts and felt pretty good about it.

I then looked into TIG welding. And I was impressed. Much cleaner and better looking welds. I ended up taking the EAA course in TIG welding and got a nice Lincoln tig welder. After a few weeks of practice I am finally getting the hang of it and now plan on TIG welding my plane.

As others here have said, both methods will work fine. They are both proven with each having many years of construction history behind them. Here are a few of my observations about the two.

Gas is cheaper to get setup. And is a very common and proven method of construction. Gas can be difficult in large cluster areas where there are a lot of tubes, this produces a large heat sink effect and it can be difficult to get enough heat in there. There is also a lot of post weld cleanup with gas.

TIG is more expensive to get setup, but will produce much nicer looking welds. The welds with TIG require almost no after weld cleanup, however they do require more pre-weld cleaning than gas does. And TIG does not have as much of a problem with welding large clusters as gas does because the heat is more concentrated.

Ultimately, if you decide to go with TIG, you should learn to gas weld first, at least this is the common recommendation. The reason is because gas welding is a little easier to pickup from the beginning, and the skills you learn in gas will transfer directly to TIG.

Do not use 4130 rod to weld 4130 unless you plan on heat treating the entire fuselage in an oven. The reason that the other rods exist is because the process of welding changes the structure of the metal. Using 4130 rod will make the welds too brittle without a heat treatment. The rods that are designed to weld 4130 have alloys that produce a nice strong weld, without having to heat treat the fuselage after welding. This applies to both Gas and TIG. Be sure to select the correct rod for the process that you use.

And be sure to do your own research into which ever method that you choose. I have found that there are a lot of subject areas in welding that some people will tell you that you have to do something one way, and another group of people will tell you the opposite. One of those areas being post weld heat treating. Read the FAQ at Lincoln Electric for their opinion on that: http://www.lincolnelectric.com/knowledge/articles/content/chrome-moly.asp For the record, I dont intend to "Normalize" my weld areas after TIG welding. More damage can be done trying to do that, than what you are trying to correct.

Another good reference for some airplane welding information is the FAQ on the 2wings web site. http://www.2wings.com , click on "FAQ Files" and then click on "Welding Related". The information there is TIG related and a lot of it is from Kevin Kimball.

#### StRaNgEdAyS

##### Well-Known Member
On normalising

Waaaay back when I was working as a heat treatment operator in a foundy we used to have people bring projects in for us to put into the ovens for stress relief and normalising. Since this operation could usually be carried out in the course of normal activity, the charge for this service was usually a nominal quantity of throat lubricant, usually Scottish whiskey, since Jamie (the foreman) was a crazy Scot.
It might be worth your while to approach some of the larger foundries in your area and enquire about such services.

#### ZENO

##### Well-Known Member
Welding

I've never heard anyone say don't use oxy acetelene on airplane frames.

I've used Smith torches for a billion years because the controls on the handle are in front of your thumbs rather than behind them. As your getting along in into the thicker part of a cluster you can increase your heat one handed without stopping. They also have a great choice of tips for the thin walls we use.

I've seen people use storches that I'd use on boiler plate.

My favorite advice to people building airplanes is, "Your building an airplane not a piano."

#### ZENO

##### Well-Known Member
More on welding

Wicks aircraft sells a box of various cutoff 4130 tubes for about $20. You can use these to practice on. There are some pretty good videos available from EAA and Welding Depot.$20 or so each.

Welding is well worth learning; it's the 'carpentry' of steel.

ZENO

#### ZENO

##### Well-Known Member
welding

That's a new one on me, but it looks great.

The forward controls is just great when you have to keep varying the heat on a bead.

ZENO

#### ZENO

##### Well-Known Member
Welding

Buy a video. All projects have brackets and such to make; start with these and then work into the empenage pieces.

Getting the puddle isn't hard, moving the puddle isn't hard. It's the speed of advance and the filling in with the rod that takes time to learn.

Get started! Have at it, as one of the guys said.