Mig Tig or Arc - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 106 (permalink) Old 10-02-2004, 05:31 PM
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Gentlemen,

I'm a new guy...I have a Giulia Super in the works. As far as the Mig vs Tig debate goes - I would say if you have the $ go for the Tig, hands down the best alternative for fine work (small welds that minimize on post finishing). Mig just adds too much filler and you just don't have the heat control for 1mm sheet metal. Good luck either way!
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post #17 of 106 (permalink) Old 03-28-2005, 01:22 AM
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What kind of welding you do depends upon the craftmanship level you desire.

For outside panels, everybody seems to forget about gas welding. Hammertack gas welding will produce the least warpage of all, and the welds are mallieable.

For welding inner panels, floors, etc. a good mig welder should do fine. Be sure to choose the correct wire and shielding gas for your application.
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post #18 of 106 (permalink) Old 03-28-2005, 02:39 AM
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Quote:
Originally Posted by jbrown006
What kind of welding you do depends upon the craftmanship level you desire.

For outside panels, everybody seems to forget about gas welding. Hammertack gas welding will produce the least warpage of all, and the welds are mallieable.

For welding inner panels, floors, etc. a good mig welder should do fine. Be sure to choose the correct wire and shielding gas for your application.
I have to agree ... I have returned to using Gas more and more with the boot lid work I am currently doing. MIG is great but the control you have using Gas is amazing and as my confidence returns my welds are so good that I do not even need to grind them off.

Welding is all about the users skill, not the choice of welding machine ... and patience

Pete

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post #19 of 106 (permalink) Old 03-28-2005, 01:37 PM
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Mig!

Having become fairly skilled with a MIG unit over the past 4 years, I vote for MIG. You can buy one at any Home Depot, and they are cheap and very easy to use. However, to use one skillfully takes a lot of practice at learning how subtle changes in heat, wire speed, time of arc bursts, steadyness of hand, etc. can change the finished product. Also, get the carbon dioxide/argon mix when you get gas, gives best results.

One thing people forget about TIG when they promote it is that a TIG is essentially a bench welder. Does a superb job, but you need two hands (one to strike an arc, one to feed the wire) and a foot (to control the heat). Renders them VERY impractical for any kind of welding under a car.

One of our ambitious but often clueless friends got rid of a superb MIG unit and bought a TIG, touting its superiority. He quickly found it next to impossible to weld underneath his car due to the two hands and a foot requirement.
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post #20 of 106 (permalink) Old 03-28-2005, 02:12 PM
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Just get them all .

I have an Arc, MIG, Spot and Gas welding machines/sets ... just missing out on the TIG.

I use the MIG for tacking and alot of panel work. It is fanstastic for installing a (butt welded) patch ... as you have a hand free. It is also good for welding the patch in ... just got to use multiple tacks. If you try and run a weld there will be too much heat and it will distort all over the place ... and pull the panel out of shape as the weld cools

I use gas when I can get to both sides of the panel and (after tacking with the mig) I fusion butt weld ... and hammer as required while cooling. I had stopped using gas for this, but it really is great.

I hardly ever use my Arc ... I used it to make the chassis jig and race car trailer, etc. but find the MIG is used for much of this too.

I also hardly ever use the Spot welder as it is very heavy and takes a long time per spot (being single phase) ... but I do use it ocassionally when I want to do a real spot.

I enjoy welding and it really is something that gives me a degree of self pride ... call me simple, but yep I get something out of it ... and confidence really helps the process.

Keep at it ... we can all get better, and all our Alfas benefit .
Pete

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post #21 of 106 (permalink) Old 03-28-2005, 06:55 PM
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I bought a MIG welder because it has versatility and is easy to learn. After practicing a bit on scrap metal, I'm about to do my first welds on the Alfa.

MIG welding sheetmetal using butt joints is not difficult. As mentioned, it does take some experimenting to find the right settings for amperage, wire feed speed and aiming the gun.

It's important to carefully trim the metal that is being welded together for a close fit. Also, the two panels must be thoroughly clamped so that they end up flush when the weld wire gets shoved at them.

Bill / 1977 Alfa Romeo 4C2000 / 2012 BMW S1000RR / 1975 BMW R90/6
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post #22 of 106 (permalink) Old 03-28-2005, 07:25 PM
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How the professionals do it (Ferrari Spider hard top):


Picture from www.tomyang.net

Pete

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post #23 of 106 (permalink) Old 03-29-2005, 06:14 PM
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Can anyone suggest a good weld wire for MIG for outside sheetmetal that is easier to grind? The stuff I'm using is conventional steel weld wire and it takes forever to grind off. Also, what is a good wheel to use for grinding?

Thanks for any tips.

Bill / 1977 Alfa Romeo 4C2000 / 2012 BMW S1000RR / 1975 BMW R90/6
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post #24 of 106 (permalink) Old 03-29-2005, 07:51 PM
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Quote:
Originally Posted by Bill77
Can anyone suggest a good weld wire for MIG for outside sheetmetal that is easier to grind? The stuff I'm using is conventional steel weld wire and it takes forever to grind off. Also, what is a good wheel to use for grinding?

Thanks for any tips.
Bill,

I actually use a cut off disc for grinding off MIG welds ... this allows the disk to flex a bit and well I just find it easier. Not sure if it is the quickest method though.

Also I have always found Norton grinding disks to be excellent ... but can't get them anymore for some reason (in Sydney).

Pete

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post #25 of 106 (permalink) Old 03-29-2005, 08:57 PM
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Quote:
Originally Posted by Alfajack
One thing people forget about TIG when they promote it is that a TIG is essentially a bench welder. Does a superb job, but you need two hands (one to strike an arc, one to feed the wire) and a foot (to control the heat). Renders them VERY impractical for any kind of welding under a car.
I agree, but I also do TIG welds with a finger control (moves the foot control to a dial on the handle) which allows me to get into many very tight spots comfortably.

still for whacking out some quick repairs while the car is on jacks, I could'nt see any reason not to MIG.

'62 Giulietta spider --- '74 spider rolling chassis--- '64 Giulia Ti --- '6o's DUCATi 250cc cafe racer.


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post #26 of 106 (permalink) Old 03-30-2005, 02:41 AM
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Quote:
Originally Posted by PSk
Bill,

I actually use a cut off disc for grinding off MIG welds ... this allows the disk to flex a bit and well I just find it easier. Not sure if it is the quickest method though.

Also I have always found Norton grinding disks to be excellent ... but can't get them anymore for some reason (in Sydney).

Pete
Thanks for the info. I'll pick up some more cut-off discs today. Maybe they will have Norton at the local Production Tool Supply store.

Bill / 1977 Alfa Romeo 4C2000 / 2012 BMW S1000RR / 1975 BMW R90/6
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post #27 of 106 (permalink) Old 09-11-2005, 06:46 AM
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I may be a bit jaded on this subject based on my job history, but......

I am the Quality Manager for a division of my company which does a lot of welding in the factory, as well as a GTV6 Owner. The MIG process is probably the correct answer for many of the reasons already mentioned, but keep in mind that welding thin materials without distortion is not a task for a novice. Even experienced welders can have difficulty with such a weld joint.

In short, welding on cosmetic surfaces might best be left to somebody who has plenty of experience with this type of welding.

My GTV6 restoration needed zero body work, and just a small amount of weld repair on two rusted areas, and I really spent the money to get it in nice shape. You may want to find a car with less body repair needs to begin with.
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post #28 of 106 (permalink) Old 09-11-2005, 09:36 AM
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hutchensgd,
I agreed about saying away from the cosmetics until the novice gets some experiece under their belt. I though, have had a different experience with the professional welder.

I took over the management of the weld shop as part of my duties about five years ago. Trained as a machinist, I didn't have a lot of welding experience.

One day the welders were working on some very thin sheet metal, which in our large shop does show up very often. Seeing the work sparked my curiousity. I called the lead man over and after we talked about the work for a bit, I asked this question. What is the thinnest metal the shop can weld?We finished our conversation without him really answering the question.

About a hour later he showed up in my office and stuck out his hand. Here you go, will this do? In his hand was two gum wrappers (Doublemint stick
kind) welded together. I was speechless.

Some how those wrappers got away from me; but, I'll never look at a stick of gum the same way. I also never take the talent of my man for granted (not that I ever did).
George

[B][I]George[/I][/B]
[U]Current Stable[/U]: 65 Giulia spider/03 Audi A6 2.7t BiTurbo 6spd.
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post #29 of 106 (permalink) Old 09-11-2005, 10:21 AM
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To All,

Regarding the use of a Mig welder on the outer sheet metal, one would want to use .025" or .020" (smaller is best) wire with the Carbon Dioxide/Argon (75%/25%) mix. This will give best control and least "weld spatter" (those little metal beads stuck around the weld).

.030" Mig wire works best for chassis.

Mig has another advantage in that it is more tolerant of pollution in the weld area such as a (minimal !!) ammount of undercoating, grease/oil, paint and galvanizing.

Torch is indeed best on outer panels but takes a high degree of skill that many are not able to obtain in a timely fashion.

Tig works well but is brittle. Use coat hangers for welding rod because they are made of very soft steel.

Cheers, Paul V
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post #30 of 106 (permalink) Old 09-12-2005, 09:45 AM
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I have to interject here regarding Tig...The statement of Tig welds being brittle is completely false. They would indeed be brittle if you use coat hangers as filler! Coat hanger wire is the crappiest steel there is! The chemical composition is all over the place. I would stay away from anyone who would use coat hangers for welding work on your project! For reference, have a look at any of the Ron Covell videos on metalworking...

Bald Italian guy with a weak spot...or two...
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