Basic Welding Question

Yes Mig works well.  Since you have no experience, I would STRONGLY  suggest you take a basic welding course at a local Community College or trade school.   It will be the best way to insure good welds.  You must be able to not only weld, but you must also be able to look at your weld and tell if its good or not.  You will also learn to heat some type of joints to stress relive them. Also how to set up your welder as far as power you should use and wire feed speeds etc.

I prefer Tig cause it makes such pretty looking welds, but Mig is really easy once you learn it.

Thanks, I was planning on taking a course, but wanted to make sure that the end result would allow me to build my airplane, not result in me needing to take another course to learn to Tig weld.

While some production aircraft and kit planes are MIG welded, they are done so in a factory setting, using $$$ equipment and trained people.  Your average garage shop MIG welder will not do work of sufficient quality for aircraft work.  You don't need to spend a bucket of dollars on a TIG machine either.  Gas welding is a perfectly acceptable method of aircraft welding and is neither expensive nor extremely difficult to learn.

Jeff is correct.  A "cracker box" Mig Welder from Harbor Freight is not suitable for 4130 welding.  Cheapest and easiest to learn is Gas Welding.   Slower, but it is really satisfying in a personal kind a way.  If you decide on gas, it is VERY important to make sure your regulators will function in the 3 to 4 psi range.  Most "off the shelf" regulators have trouble at those low pressures.  They will click on and off. So, just tell your supplier that you will be welding 4130 and such and will have occasion to run the pressures in those ranges.

In my experience Mig welding on thin wall tubing can be a real challenge. The biggest problem is proper amperage control and most low end machines have four basic settings which just isn't good enough. You can get a high quality 200-250 amp TIG machine on-line for a couple thousand dollars that will gives a much, much better job (with practice).

Of course welding is only part of the equation. Proper pipe fitting is equally important and that's a skill on it's own.

"DITTO"

Good luck welding .030 wall tubing with MIG or TIG. Welding inside the crotch of a cluster with a tig torch can be a bit of a challenge.

Since you will need a torch anyway for forming, bending and stress relieving buy a good torch and learn to weld 4130 with it. Buy a Smith airline torch and regulators. A quality torch makes all of the difference in the world. Forget all of the fancy tables relating regulator pressures and torch tip sizes. Open the torch valves and set both regulators at 10 PSI with gas flowing, close both torch valves and you're ready to weld. Select the tip that gives a good flame without too much flame velocity and melt some steel.

Save the TIG machine until you get ready to weld your stainless exhaust system.

I attended the gas welding SportAir Workshop in Oshkosh this past weekend, and the subject of MIG welding came up.  The short answer is that it's a bad idea unless you have a lot of experience.  There is a good chance that you won't have fusion between the two pieces.  The instructor detailed the circumstances under which he would be comfortable overseeing a MIG weld operation for a 4130 airframe.  The list of requirements was quite long and included the creation of Weld Procedure Specifications, destructive testing, and a whole lot of crap no one wants to deal with.

Luckily, oxy-acetylene gas welding is easy to learn and well suited to airframe construction.  I went in to the class without any experience and walked out confident that after more practice I could safely weld up an airframe.  Most of the equipment can be purchased used, and even new it's not terribly expensive.  Compared to TIG, it's downright cheap. 

Since you're in Georgia, you may be interested in this workshop in Griffin.  I have no experience with TIG, though it's on my list of things to learn:

http://www.sportair.com/workshops/TIG%20Welding.html

The instructors in my Oshkosh class were experienced and knowledgeable.  Highly recommended.

Ok, expense is a concern.  Buying a $2k TIG welding machine is not something I can reasonably purchase to start.

A few hundred on a Gas or Mig weld setup is something I think I can swing.  I asked about MIG simply because I have no welding experience and heard it was the easiest to do and I heard that TIG was the hardest.  What are your recommendations as to which to start with if your goal is to weld an aircraft frame for Rag & Tube manufacturing?

I can't speak with any authority, as everything I know about gas welding has only been in my head for about 72 hours.  That said, I'll tell you what I learned from those that know more than I do.

First, I would recommend finding a competent instructor with experience welding aircraft.  You're going to fly in this thing, so you might as well do it right.  The EAA SportAir Workshop was great, though they seem to occur somewhat infrequently and are in high demand.  If that doesn't work out, an EAA Technical Counselor may be able to point you to a local instructor or community college program.  Worth a shot.

Second, you'll need some reference material whether you teach yourself or learn by other means.  This EAA book/DVD combo looks good.  I have the book but not the DVD.

Finally, you need the equipment.  You're going to need a torch, tips, hose, regulators, tanks, and eye protection at a minimum.  I was able to try two torches this weekend - a Harris torch, probably this one, and a Meco Midget.  The experienced welders seemed to favor the Meco for its fine control and light weight.  Other options include Smith and Henrob.  I'm probably going to purchase a Meco Midget with a lightweight hose.  The Harris torch with the bigger hose can be cumbersome in tight spaces.  Regulators and tanks are still a mystery to me as I haven't done much research on that yet.  From what people have told me, the largest expense is going to be the tank/regulator combination, which I'm guessing will be more than $100, but less than $500.  Goggles or a face shield with a #5 shade should be inexpensive.

That's all I've got for now...

Another thumbs up for the Meco torch.  It's a great little unit and easy to control the flame. 

You can put together a basic gas setup with torch, regulators, gas bottles, etc etc for around $5-600.  Plan on a little bit more for a better torch like the Meco, maybe $7-800 for the whole deal.  Still many times less than a tig machine, and more versatile.

I've attached a couple pics of an early welding project of mine. I bought a Sears Mig welder and tried to weld up a set of headers from thin wall mild steel tubing and had a lot of problems with burn though. The other problem I had was that the tubes were not well fitted which meant I had to fill gaps with welds. It works but isn't pretty. I learned a lot from that project. 

Gas is a perfectly acceptable way to go and is relatively easy to learn. Tig is similar to gas but just uses an electric "flame." The biggest thing that you need to watch out for is excessive heat. Also, as I previously mentioned pipe fitting is extremely important. taking the time to make sure that everything fits properly will pay big dividends when it comes time to do the welding.

I used to woodworking, where you have to get a perfect fit, or extremely close to it.  The idea of 'leaving a gap to fill' is just a foreign concept to me.  Since most of you have more welding experience than me, would you suggest, leaving out the monetary concern for startup, that I consider learning TIG to start, or is that 'just to much for a first time welder'?

The basic technique of tig and gas are pretty similar so learning one will help you with the other. With tig you will have to learn in addition to your gas technique proper amperage control, gas flow (easy enough), electrode types and preparation and how to properly hold the arc. I wouldn't say that it's "too much" but it probably wouldn't be a bad idea to start with gas, learn proper technique with it and when you are comfortable with that then move on to tig if that's where you want to go.

Ultimately in any case learning consists of about 30% theory and 70% practice, practice, practice. The more I weld the better I get at it.

Here's a web site loaded with instructional videos about welding: http://www.weldingtipsandtricks.com/welding-video-archives.html

If you are going to scratch build an airplane & appreciate good tools, why not buy the best for the job?  Lincoln & miller both make TIG machines for less than$1500 (internet) that will do any aircraft welding you will ever need to do, including aluminum.  I think it's easier & quicker than gas & you will appreciate the quality & appearance of the weld.  Forget the MIG. You wouldn't do cabinet work with a skill saw, would you?

Well, I have done cabinet work with a skill saw, but I think that is beside the point.

I hear you can gas weld aluminum to.  Even thin aluminum with the right torch.  It's not about the technique you use, but the tools and the skill.

I'm not opposed to using TIG, but money is an issue for me.  Can you provide a link to the $1500 TIG setup you referred to?

Take a day or two and go to Sun-N-Fun and talk with the guys at the welding tent. You can get some "hands on" welding instruction for FREE and they are usually offering equipment (tig) at a pretty good price delivered.

Also, there are a number of welding forums online and the moderators/members will be able to make suggestions as to what types of  equipment will do what you require.

Like you, I am interested in building a tube and fabric airplane, but am still sitting on the sidelines due to lack of workspace.

Greg,

Whatever the cost of the tig unit, keep in mind that you'll have to add the cost of a gas rig to your cost.  There are plenty of areas that you'll need a torch for (bending and heat forming for example) that just can't be done with a tig machine.  If you tig weld you still need a torch, but the reverse it not true.  You need to factor that in when doing the $$$ calculations.

The number of posts would seem to indicate there is really no basic welding question!