Mig or Tig welder...

[d.j. moordigian]

Steve,

I should have qualified my statement with this..

1. If you can gas weld, you mite be able to TIG.....go practice on a friends machine.
2. Kevin is correct about seeing. I'm far sighted, I use 1.75 cheaters for reading
a mic., 3.00 for welding, and sometimes that's not enough! I sometimes wear BOTH
pairs at the same time($%its getting old), you need to see what's going on.
3. If you do buy a TIG machine, have the company prove to you that it can weld
Aluminum beer/soda cans. A machine with all the bells and whistles is no good if
you can't weld light stuff.

[d.j. moordigian]

Popeye & Bob,

You sure? I use 75%/25%, Argon/Co2. Oxygen will contaminate the weld...

[Bob C]

I thought the same thing Dudley. When I bought my MIG I went to the weld shop at work
and asked the foreman what gas to get and he said tri-mix. I always thought the shielding
gas was to keep oxygen away, learn something new all the time. Check the link to Praxair
http://www.praxair.com/praxair.nsf/7...a?OpenDocument

Bob

[d.j. moordigian]

Bob,

That's interesting. I have used the tri-mix on SS with MIG on a large hopper, didn't
like the end product, did the rest of the job in Tig(about 90% worth). The tri-mix,
I think is more money than the 75/25, and it works and looks better than Co2.
Thanks for the info!

[Popeye31]

Ive worked at shops that use 60/40 and 75/25 so either one will work. and your right about the taking the oxygen out of the equation makes a stronger weld. also down here we set the regulator at around 35.and when you are welding overhead a little higher. but it may be different with your machine and regulator so these are just good starting points.

[Bob C]

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Originally Posted by Popeye31

Im a ICAR certified autobody mechanic of 17 years. ICar is the equivilant of ASE in the mechanics field Im also ASE certified. and the standard in any body shop is mig with 60/40 argon/0xygen mix. Tig is also accepted but most shops don't have them because of the expence and most of the body men don't know how to use them.There are lots of mig machines out there.also ICAR does not whant you to use a flux core machine. the welds are not as good. welding on sheetmetal is different than welding on a nise 1/4 in plate, the metal is thinner and requires cool down between welds or I should say tach welds. once you practice on a few pieces of scrap to tune your machine to the metal you are welding than put the patches in . don't skip the test panels if you do you will probably end up with a realy warped door skin ,back panel, and cowel panels. and will need to put way more bondo than is nessasery for the repair.

So did you mean 40% CO2?

[Flop]

tig tig tig . mig is great for tacking in panels and dirty work but if you wanna do sheetmetal tig is your best bet in my opinion.for heavy steel its nice if you wanna get pretty with your welds . also its nice for stainless trim and aluminum. the extra money is worth it if you are going to use the machine for all 3 varieties of metal and hell even exotic ones. . dont forget 100% pure argon for the tig in most common instances.

[d.j. moordigian]

Vince,

The shop next door has a new Lincoln with dip and pulse, all the gadgets. It's a
very nice and expensive machine, but it doesn't weld good at low settings and
the arc won't stabilize before you blow a hole in the part. Were talking thin stuff,
.020"-.030" with a 1/16" Tungsten. The Reps. have looked at the welder, changed
boards, adjusted this and that, still the same.

OK,...the beer can thing mite be overstating the importance, but I like Steve and
it's an expensive investment. I hate to see him get a welder that won't do FINE work,
but does great work on his tractor. Make sense?

[PetesPonies]

I posted this the other day and it's gone?? I wanted to show you how a good MIG welded patch can look. First pic is the patch just tacked in a couple places to get leveling correct. The second pic shows the finished patch. At this point, nothing but a ground weld bead and cleaned up with a coarse disc on a DA. Whatcha thunk????






sp the point of this is . . . sure a TIG is best, but is it always needed?? No . . you just have to know how to MIG weld . . correctly. And by the way, this is butt welded in, no overlapping. There also is no backing material used. No copper or such. Not needed if you "CAN WELD ".

[d.j. moordigian]

Vince,

Yes, read web page. The Lincoln Invertec with a pedal and cooler. In my youth I
had an air cooled torch, too bulky. GOOD info on your sight, as always.

[Flop]

only problem in my opinion with mig is you cant hammer them too much . they will crack .

here is a panel done with a tig - Miller synchrowave 250 . i dont know why people are bashing a welder with high amps ... i can weld the thinnest of sheetmetal or 3/16th plate with the turn of a knob.


the tig likes those gaps tight!



all welded up

[Roadster62]

Beautiful Flop, when you turn out first class work all others are second rate. Bob

[RockHillWill]

I have no intention of stirring up the pot from a technical standpoint, only that I have been doing a lot of studying lately regarding this TIG vs MIG vs Gas welding, and have the following OPINION (only!).

It is my 25 year personal experience that MIG welding on sheet metal, while done as nice as any of the methods has the greater tendency to crack from vibration. I used to build race cars, and no matter the way it was welded and by whom, it would ALWAYS crack somewhere to some degree after each race. No problems with the structural items that were MIG welded.

I have interviewed very knowledgeable folks from one end of the country to the other for an answer to this issue. They did not all agree, but all were happy to express THEIR perspective. TIG welding is much more forgiveable as regards sheet metal resistance to cracking, but the best that I have experienced personnaly is the gas welding. I am very good friends with a gentleman that has gas welded aluminum race car bodies for 42 years, and it is his opinion that gas welding is the better choice for welding sheet metal if your intention is to use it in a vibrating envirinment.

It is our opinion that this tendency to resist cracking is due to the fact that gas welding forms / allows a more ductile weld. I understand that filler material has an effect on this issue, but i believe it is not the predominant factor.

What I have formed as an OPINION at this point is that the slower rate of the gas welding and the lower pressure afforded by the HENROB style totches allows/permits the nearby metal metal to spread the heat over a larger are adjacent to the weld (HAV= heat affected zone / blue area). This slower heat migration expands the metal while hot, but shrinks back beyond its original position. This is why you 'hammer weld'. You are stretching the metal back to it's original thickness.

You can confirm this on your own by only looking at the HAZ width with the different types of welding. The wider HAV is happening because the gas welding is slower to cool resulting in maintenance of the metals ductility and resistance to cracking. You can get furthur input if you use a Rockwell hardness tester to review the metals hardness (tendency to crack) near to the welded area.

So, it is only my OPINION, that you can get suitable welds with any type of welding process, but if you are welding something that is in a vibratory invironment (race car, Model A, etc) that is used over a long period of time, you would be wise to consider a method that maintains the metals original ductility. MIG and TIG are great, rapid welding proceedures, but I would sure consider the GAS Welding method if you have the opportunity. It is also,by far, the least expensive.

[Ross/Kzoo]

Very, very nice work. I don't see any discoloration on the panel where they are joined.

[PetesPonies]

Fordgarage . . what?? It's called penetration. When I grind off the high parts of the bead, I am left with the original THICKNESS. I do not grind out the weld, the penetration shows from the backside. My welds typically go all the way through. That's one benefit of butt welding. I';m not sure why you are implying anything negative Ford, you are supposed to understand welding, right? So don't imply that a MIG cannot do a good job. What an unbelievable statement from someone that SUPPOSEDLY knows what he is talking about. A puddle is a puddle, regardless how it was created. There is no reason you can assume better penetration from a TIG, none what so ever.

[PetesPonies]

Flop, you seem reasonable and knowledgeable. Yes, hammer welding is more difficult with a MIG, no doubt. I end up using a skim coat of filler ( after sealing the weld joint ), I have no problem with that. Anyone that thinks that is a problem, is not knowledgeable enough in that domain. Your welds look great, but they were TIg'ed

[Roadster62]

Please explain "sealing the weld joint" for us common folk. You need Bondo, Flop doesn't, why? Bob

Originally Posted by PetesPonies

Flop, you seem reasonable and knowledgeable. Yes, hammer welding is more difficult with a MIG, no doubt. I end up using a skim coat of filler ( after sealing the weld joint ), I have no problem with that. Anyone that thinks that is a problem, is not knowledgeable enough in that domain. Your welds look great, but they were TIg'ed

[CWPASADENA]

I have been doing restoration and fabrication work for almost 60 years. When I first started out, I bought a used OX set up and thought I had died and gone to heaven. I welded fenders, frames and all sorts of stuff and with practice I got to where I was making very good welds. At the same time, I was also studying to be a Mechanical Engineer. As part of my schooling, I took Metallurgy and also a very comprehensive hands on course in welding so I not only understood how to weld but also how metals react during the welding process.

For many years, I ran my own shop where we did custom fabrication, race car work and production welding. I have TIG, MIG and OX in my shop and they all have their place. I use TIG the most and OX the least but several years ago, I did restore a vintage race car that needed major work on the frame. The frame was originally welded together using OX. While I prefered to use TIG the repair work, the car was very valuable and the customer wanted everything as close to original as possible, I welded everything with OX.

You can do very good welds with MIG on some materials, but it is much easier to do high quality work on a much greater variety of materials with TIG. With TIG, I weld everything from very thin sheet metal to heavy castings and forgings and even suspension, steering and brake components but you have to understand what you are doing. A good class in welding is strongly recomended.

A good TIG machine will do everything a good MIG machine will do and a lot more. IMO, if you buy a MIG machine now, the time will come when you will want more capability and will be looking at a TIG machine. I think what ever machine you buy, you will also need an OX set up. If you do buy a TIG, get a good machine with water cooling. If you are on a budget, I would get a OX set up now and then buy a TIG later. You can do a lot with OX.

This is what I think.

Chris

[PetesPonies]

Chris, I'm with you. I learned to weld with an OX setup. It made everything else ( other welding) seem easier, being able to control the puddle so well and learning from this form of welding. You really learn a lot being able to weld with an OX. I am not as good as some who can do what I would call, incredible, work with a gas setup. Small torches, hammering as they go . . that's impressive. No doubt, the advantage of a MIG is speed, easy setup, pretty good heat control . . . . . just all in all an easier form of welding to learn. However, my gripe is short cutting the ability to make good welds, proper welds, with a MIG. Just because you saw someone, a hack, stick two pieces together with a MIG doesn't mean all MIG work is that way.

Here here for the gas welders out there!!

[PetesPonies]

Roadster . . from a practical approach: sealing a weld ,IMO, is very important. I don't want moisture to get to my weld. Understand, my experience is mostly with 50s- 80s car restoration. We are talking about vehicles put together differently than an "A", used differently and cared for differently. Bottom line, these cars may get wet, may get driven on a semi daily basis, may see conditions you wish your car never saw. Therefore, as I said, I want no moisture getting to the weld. Most times, filler is used over the weld to smooth it out. The amount depends on the repair , who did it etc. But still some is used. I use a "paint" to cover the weld, both front and back. This paint is a urethane that has great adhesion. I use it first on the welded seam, before filler goes on. Typically filler is polyester based. But it contains talc. When moisture gets to the talc, it swells and bubbles. You have all seem that. If I seal the weld, I make sure there are no pinholes that "could" leech moisture into the repair possibly from the backside. But I seal both sides to be sure. I have been doing this a long time and find it gives me exactly what I expect, a trouble free repair.