# MIG vs TIG re: Kitfox use MIG?

Discussion in 'Tube and Fabric' started by Zoomzoooie, Mar 30, 2011.

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1. Jan 30, 2012

### Zoomzoooie

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I'm only referring to information from welding tutorials and what seems to be the consensus. Since which ever process I will be using, I will have to practice to become proficient, so I am trying to gather as much information about the processes as I can.

TIG and O/A allow for heating the area allowing it to come fully to temperature before filler is applied. MIG starts filling as soon as you strike the arc while the area is not fully heated and this is where they say there is not full penetration. This may not be the case with thinner metal.

TIG can allow the area to cool some after the filler is removed and O/A is even better removing heat slowly by taking the flame away slowly to keep from shocking the metal to better prevent metal failure around welds.

I think if I was proficient in MIG and had a better machine I would not be afraid to use it. By what you are saying about MIG, you need to know more what you are doing then with TIG or O/A and have a better machine to do it.

I'm not condeming MIG, I'm simply stating information about the process which seems to put it at the bottom of the list for aircraft application. Car builders don't have to worry so much about metal failure since they are using 10x the metal thickness.

ZZ

2. Jan 30, 2012

### JIC

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ZZ, On a tight budget, stick with Oxy/Acty. Cheaper, easier to learn, and with a little practice you can make aceptable
welds. I have welded two, starting on my third, fuselages using only Oxy/Acty.
I tried mig once, found it to be difficult to get into the tight places with the mig torch.

jic

3. Dec 5, 2012

### Rosco

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Just a little tip to stop shock cooling at a welded joint,make a bag and or sausage out of fiberglass fiber,loosely fill with lime and sew shut.When wrapped around a welded joint it slows the cooling down a lot.Small welded pieces immersed in lime will stay hot for hours. Cheers Rosco

4. Jan 12, 2013

### Pops

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If you have the mindset of doing things the quick and easy way, please don't build an airplane.
Gas or Tig only for me. Weld in my shop everyday on aircraft building.
A neighbor of mine made a somewhat hard landing with a Kitfox, lots of failed welds in the lower fuselage. Pops

5. Jan 12, 2013

### BBerson

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Can you provide pictures of these so called " failed welds".
Most thin wall aircraft tubes will fail just outside the weld after a hard landing. It hardly matters what type of weld process was used.
Gas Metal Arc Welding ( MIG) is FAA approved. ( see AC 43.13)
Yes, GMAW can be fast, but it is not easy on thin wall. For success, it takes considerable skill, practice and weld science knowledge, same as any other weld process.

6. Jan 13, 2013

### harrisonaero

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If you watch Earl Luce's excellent welding video he talks about a MIG welded fuselage from a "major kit manufacturer" that had something stacked on it while shipping the fuselage and a majority of the welds cracked in the HAZ just outside the weld.

7. Jan 20, 2013

### Pops

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The MIG welds that the FAA approves are not from the machines that the average builder can afford, and the skill level above the average aircraft builder. I would NOT advise anyone to use a MIG and would not fly in the aircraft.
I have been welding aircraft tubing since 1970 and also certified for high pressure steam vessels,( coal fired power plant boilers, all 100% x-ray) since the mid 70's and I weld 4130 making aircraft parts in my shop almost every day, so I know a little about a bad weld.
Yes, the welds broke on the Kitfox, but I did not take pictures, wasn't my aircraft. Pops

8. Jan 21, 2013

### BBerson

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The FAA does not approve welding machines. But yes you are correct, a proper machine is needed. A large size machine is not needed or desired. For home use my Miller 135 is almost ideal and has automated control and welds very nicely (about $700 plus gas bottle) I am not suggesting that a$99 flux feeder will work well, it won't.

From your comments, it sounds like you have no MIG welding training or experience with aircraft parts, yet condemn a method used by many major airframe companies.

9. Jan 21, 2013

### Pops

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Read again, I did not say that the FAA approves the machine, I said welds. They will approve the weld.
The first time that I used a Mig was in 1969 and have several thousands of hours welding with a Mig as a Journeyman Millwright in a major auto plant building robots and later designing robots as a ME and also as a Journeyman Boilermaker all welding with Mig, TIG , Stick, and some gas welding. Also have worked as a construction Pipe Fitter, Sheet Metal Worker, Electrician, and retired Com. Pilot flying for the U.S. Gov.
I understand the pro and cons of a MIG. It has it place, and the best place for a MIG is not welding aircraft tubing.
Yes, Miller makes good welders, I use Miller for TIG and Stick in my shop. Pops

10. Jan 21, 2013

### BBerson

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I never heard of any FAA inspector approve a weld. (40 years experience in aircraft industry).
But I can see your opinion is not likely to change.

11. Jan 21, 2013

### Pops

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Starting a new aircraft Company welding certified tube fuselages , the FAA will want to look at the welds, you can bet on it.

BTW-- Do you always talk down to the little people with a superior attitude, and publicly doubting ones integrity without knowing anything about the person, like in a previous post saying "So Called". Also your statement in your last sentence. That is completely uncalled for in holding a friendly dialogue.
IF this is your normal way of talking to people, please do not answer any of my post and I will not answer any of yours. Thank you. Pops

Last edited: Jan 21, 2013
12. Jan 21, 2013

### BBerson

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I don't need to, I was the production manager at a small airplane factory (Type Certificated)that used MIG.
The FAA never looked at or tested any welds
As I said, MIG welding is approved and widely used in the aircraft industry.
There is no evidence to support your claim that these certified aircraft are unsafe.

edit: I used the words "so called" because I didn't like your incorrect comments bashing the aircraft MIG welding industry and simply asked to see some evidence.

Last edited: Jan 21, 2013
13. Jan 21, 2013

### BBerson

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This is from EAA:

MIG Welding for Homebuilts

Q. In most of the articles I see in Sport Aviation, I see builders using gas to weld tube for aircraft fuselages. I recently bought a Lincoln 220V wire-feed MIG welder for a business venture with the thought that, at some point in the future, I would be able to use it to build other projects, one of which might be an airplane. It will accept a gas bottle for shielding although I have not used that option yet. Can this type of welder be used to weld tubing in an aircraft fuselage?

Yes, a properly welded MIG (GMAW) joint will be more than acceptable for an aircraft fuselage. However, amateur builders need to think about more than just the strength of a properly welded joint. MIG welding's primary advantage over TIG (GTAW) or oxyacetylene "gas" (OFW) welding is speed. From a production standpoint, speed makes MIG the preferred welding process. Speed isn't as important to homebuilders compared to price and ease of attaining and maintaining proficiency.

MIG is more expensive than gas welding but about half the price of TIG. From a cost standpoint, MIG sounds like a reasonable option, and it's probably the easiest method to learn for welding thick, flat material (just pull the trigger and go!). But for a fuselage, you need to weld thin wall tubing, and this is probably the most difficult use of the MIG process. Even experienced, professional MIG welders have difficulty the first time they attempt to MIG weld thin wall tubing.

For builders learning to weld so they can build their fuselages, learning and maintaining TIG or gas welding proficiency is easier than MIG. This is one reason why most of the articles mention these welding methods. However, because you'll be using MIG regularly in your business, all it will take is practice to be able to transition to MIG welding thin wall tubing.

In researching this answer, we spoke with Richard Finch, an aerospace engineer, Technical Counselor, Flight Advisor, and author of Performance Welding and Welder's Handbook (both available from EAA at 800/843-3612), and he agreed with the above. "The only thing that I would add is that most of the kit-plane manufacturers use MIG for speed and accuracy, but they practice, practice, practice before they turn a welder loose on a salable MIG weldment." For detailed information about the pros and cons of welding thin wall 4130 tubing with MIG, see Performance Welding.

14. Jan 21, 2013

### Pops

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I have my opinions and you have your opinions . I have just been on this site about 3 weeks and after reading the rules of this site, PERSONAL ATTACKS are not allowed. You made 3 personal attacks because you did not like my opinion.
In your world, you may get by with personal attacks, but in my world, it is not tolerated, and says volumes of a persons character. Good Day.

15. Jan 22, 2013

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