What's the Best Weld for Cracks and Patches?

[Tom Wesenberg]

I bought my Lincoln SP-125 MIG welder about 20 years ago with the idea to use it for doing body repairs on my Model A's, such as rust patches, or fender crack repair. A few years ago either Flop, Brent, or Kevin mentioned that MIG produces a hard weld. I used my MIG to repair a cast iron generator pulley with a piece missing. I thought I would file the weld to shape, but the file wouldn't even scratch the weld, so I had to use my Dremel with a grinding wheel. That's when I found out just how hard the MIG weld is.

I'm thinking such a hard weld wouldn't be good for repairing a fender crack because it would probably be so hard it would crack again quite easily. When I repaired the missing metal in the log splitter cover I decided to gas weld it, and that worked fine. So, for Model A fender patch work or crack repair, is TIG or is gas welding the preferred way to go? Or are they equal in weld quality and durability? Thanks

[Mike V. Florida]

Originally Posted by Tom Wesenberg

So, for Model A fender patch work or crack repair, is TIG or is gas welding the preferred way to go? Or are they equal in weld quality and durability? Thanks

I think this is going to be a type of oil discussion. Let me start,

http://www.secondchancegarage.com/public/150.cfm

http://fordbarn.com/forum/showthread.php?t=34119

http://www.sanjosechevys.org/Tech/te...al_welding.htm

[Manager]

My son and I were just talking about this. I'm keen to try a tig on panels. Oxy is good but you need the flame right or you can do a great looking weld and when you hammer it it falls apart. And when you don't do it all the time you take forever to get it right.And in Au the bottle rental is rediculous.So i have been using MIG recently. But you can't hammer the welds they are so hard so a lot of grinding. I have heard there is softer MIG wire now available but I havn't looked into that.

[Dollar Bill]

TIG will offer the strongest weld as you have greater control of heat/penetration than any other form of welding. It is slower than MIG but TIG will induce less distortion as the torch provides the greatest concentration of heat.

Oxy/Acetylene is best for heating and cutting - Wouldn't even consider using it for metal repair.

Lower tensile strength MIG wire is available that will be easier to grind.

[Mike V. Florida]

Originally Posted by Manager

I have heard there is softer MIG wire now available but I havn't looked into that.

Originally Posted by Dollar Bill

Lower tensile strength MIG wire is available that will be easier to grind.

http://www.esabna.com/us/en/products...oductCode=9492

[37Benny]

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Originally Posted by Tom Wesenberg

I bought my Lincoln SP-125 MIG welder about 20 years ago with the idea to use it for doing body repairs on my Model A's, such as rust patches, or fender crack repair. A few years ago either Flop, Brent, or Kevin mentioned that MIG produces a hard weld. I used my MIG to repair a cast iron generator pulley with a piece missing. I thought I would file the weld to shape, but the file wouldn't even scratch the weld, so I had to use my Dremel with a grinding wheel. That's when I found out just how hard the MIG weld is.

I'm thinking such a hard weld wouldn't be good for repairing a fender crack because it would probably be so hard it would crack again quite easily. When I repaired the missing metal in the log splitter cover I decided to gas weld it, and that worked fine. So, for Model A fender patch work or crack repair, is TIG or is gas welding the preferred way to go? Or are they equal in weld quality and durability? Thanks

as my Welding Teacher once said "you're your own welder.." There are guys who use only MIG and produce good work, There are guys who use TIG and produce good work..and then there are guys who don't have any welding equipment newer then 1949 and produce good work..to me Welding process (machines/equipment) are like shovels..what type of hole are you trying to dig? some of us have many different shovels to choose from and say which one we like better then some guys just have the beat up one they found for a $1 at an estate sale..and can dig holes around us..i know which welding equipment works well for me..because I'm me..what I do might not work out well for you because you're a different person..I like gas welding, the bodyman back when our A's were new used it..it worked then it can work now? I have a MIG welder but I only use that for welds I'm not going to grind down/or welds I can't get behind with a dolly and are not going to be seen anyway. Good Luck, Benny

[BRENT in 10-uh-C]

Originally Posted by Tom Wesenberg

I bought my Lincoln SP-125 MIG welder about 20 years ago with the idea to use it for doing body repairs on my Model A's, such as rust patches, or fender crack repair. A few years ago either Flop, Brent, or Kevin mentioned that MIG produces a hard weld. I used my MIG to repair a cast iron generator pulley with a piece missing. I thought I would file the weld to shape, but the file wouldn't even scratch the weld, so I had to use my Dremel with a grinding wheel. That's when I found out just how hard the MIG weld is.

I'm thinking such a hard weld wouldn't be good for repairing a fender crack because it would probably be so hard it would crack again quite easily. When I repaired the missing metal in the log splitter cover I decided to gas weld it, and that worked fine. So, for Model A fender patch work or crack repair, is TIG or is gas welding the preferred way to go? Or are they equal in weld quality and durability? Thanks

The order from soft to hard is Oxyacetylene first, TIG second, and MIG third. The way to have the best weld is to fuze weld it where there is little filler rod used. This is a very strong weld. Remember it is not just good enough to grind the weld, ...the weld needs to be planished too so as to eliminate any stresses caused by the heat-induced shrinkage.

FWIW, a TIG-welded panel can still be planished well, but a MIG weld cannot. Ironically, we have used MIG wire as a filler rod with a TIG torch, so the hardening process is created by the type of welder and not the welding wire.

[monto]

Originally Posted by 37Benny

as my Welding Teacher once said "you're your own welder.." There are guys who use only MIG and produce good work, There are guys who use TIG and produce good work..and then there are guys who don't have any welding equipment newer then 1949 and produce good work..to me Welding process (machines/equipment) are like shovels..what type of hole are you trying to dig? some of us have many different shovels to choose from and say which one we like better then some guys just have the beat up one they found for a $1 at an estate sale..and can dig holes around us..i know which welding equipment works well for me..because I'm me..what I do might not work out well for you because you're a different person..I like gas welding, the bodyman back when our A's were new used it..it worked then it can work now? I have a MIG welder but I only use that for welds I'm not going to grind down/or welds I can't get behind with a dolly and are not going to be seen anyway. Good Luck, Benny

Well said, Benny. I agree. Each and everyone adapts to his / her own style.

[Vin-tin]

Tom, it doesn't matter if you use Tig or a gas welder on sheet metal repairs. Proper set-up is key...and practice, practice, practice. Just when you think you're getting good, practice some more.
Did I mention practice?
I use a double strand of twisted Mig wire for Tig welding like Brent does. I've read already that you can use a Tig torch to "soften" a mig weld, although I've never tried it.

[Terry, NJ]

Tom, As Vit-Tin said Set up is key! I used to say "Give a welder a good fit up and he'll give you you a good weld"! I believe the problems that come from cast iron are because of the high carbon content in the casting. You could make a flux of lime and boric acid and "Cap" the weld to lengthen the cooling period or you could just anneal/naturalize the piece. This should soften the weld sufficiently that it can be filed. Also with Cast iron, you can feed some S.S. into the arc. I have used S.S. wire in place of NI rod with good results. The best one I ever heard of was when a friend welded a head off a Cat. Dozer with 6010. He Veed out the crack and heated the entire head to 1200 F in an oven, welded it, and annealed it. 6010 is not generally used for cast iron, In fact, it's not ever used for cast iron. Next, I'll tell you how I welded an exhaust manifold using a lot of "stringers". (Never Again)!
Terry

[Kevin in NJ]

Tig is wonderful. I use the same filler material as with MIG (ER70-S6). The silicon helps clear the contaminates and allows the metal to flow together easier. I do tight seams (hard to do at first but becomes natural after a while) and use a speck of filler rod to help the metal flow. I try to minimized the amount of rod I add. I do lots of little welds and stop frequently to do hammer on dolly correction of shrinkage. Once you get the hang of it you are doing seams that are tough to find after you are done and often need no filler or a couple of coats of a filling primer. The first time you take a TIG weld up to an edge and not have a burn back you will be impressed with yourself.

Oxy Act with a small torch and low pressure is the next best thing to a TIG. I have not done this (I do have the small torch) but you can see examples at Tinman Tech. Same procedure as tig, but you need a different rod (TIG rod does not work as ocy/act rod- it is very hard to weld nice with). Since you have a larger heat affected zone it will force you to be better at hammer on dolly shrinkage correction to maintain correct panel shape.

MIG works, but you can not do the hammer on dolly corrects like you can with the above 2 welds. The weld line is always harder and more importantly is the need to get the weld level first. This means you do a few spots then grind both sides flat. But you can not get the mig weld quite flat enough. So as you hammer the slight bulge of the weld makes it harder to get the metal nice.

Keep in mind I have a decent Lincoln SP-175 (if is remember correct) MIG welder. I freely admit I am not the best welder too.

My TIG is a 60's vintage Miller 330 A/BP that makes my meter spin real fast even on idle. It can do the thin stuff and is full of copper windings. They can be had for the $600 range.

I love tig, but if your pocket book does not for getting a quality system. A good pair of low pressure regulators and a very small tip torch with the right rod can do wonders for less.

Anyway, some ideas.

[katy]

When you're talking MIG welds are hard, are you talking flux-core wire or using shielding gas w/solid wire?

[captndan]

I use gas on sheet metal. Old fashioned wire coat hangers with the paint removed makes for a good weld. For fill I use brass rod.

[Kevin in NJ]

For MIG I only use gas.

NEVER use brass for doing body panels!!!!!!!!!

You can not correct for heat shrinkage and the flux is likely to come through the paint. Then the panel all has to be cut off to fix the brass weld.

You can use coat hangers, but the weld goes much easier if you use the correct rod. The correct rod is not very expensive and your weld quality goes up.

[Tom Wesenberg]

Originally Posted by katy

When you're talking MIG welds are hard, are you talking flux-core wire or using shielding gas w/solid wire?

I only use gas and would never use flux core wire.
A friend wanted me to weld something for him, and he had a flux core welder. I got it welded, but it looked bad compared to gas shield.

[MikeK]

Most general MIG wire is 70K tensile and a SOB to grind. There are some low alloy, very low carbon wires, in the 30K range that are soft. One is "ESAB Easy Grind". A lot of modern body shops use it 'cause they don't have an hour for someone to TIG stitch in a panel. After you lay this stuff down it is as soft as a self-annealed gas weld.

You definitely want 0.023, not 0.030 for sheet metal and unfortunately the 0.023 ESAB easy grind only seems to come in 11lb spools. About $60, kind of spendy just to try it. I have seen the 'easy grind' 0.030 in 2lb spools, but that is too heavy for most body work.

One caution- If you get a spool of "ESAB easy grind" DO NOT use it for anything structural on modern iron like frame work or unibody joints/inner panels.

[Bob Bidonde]

I recently finished repairing the sheet metal on my 190A using a Lincoln Handy MIG for patch panels, and it was not difficult to grind the MIG welds (gas & flux core).

A 0.13 diameter stop hole should be drilled through the metal at the crack tip. Doing so removes the residual strain condition at the crack tip that will cause the crack to grow. Fill the stop hole with weld.

Make absolutely sure that you have:
> A good ground connection to the welder near the weld site;
> You know what is on the backside of the weld site regarding access. The weld site must be clean bare metal on both sides. Residual paint will start a fire;
> Patch panels should have a line fit or with very small gaps not to exceed 0.06";
> Dial the MIG welder in for the thickness of the sheet metal on scrap to avoid burning through;
> Stitch the weld by tacking every inch, then go back and weld between every other tack weld until the weld is continuous.

[Pete]

As far as weld quality, Brent covered that well.
As far as what you personally want for finish, it depends on
whether you can be satisfied with second hand oats.
Mig welding is used commercially in body shops because of the
bottom line, PROFIT. Not because it is the best way to do it.
Mig weld it, scuff the welds off, fill it with Bondo and the job is
out the door before the customer has time for a second cup of coffee.

It is possible to do panels or even a complicated chop job on a late model car without ANY Bondo or lead, but, that takes lots of time.
Something only a hobby enthusiast can afford any more.

On the tech side, many people complain of when MIG welding
on sheet metal, they have blow throughs or the weld bubbles up.
There are numerous causes for this but one thing that is almost NEVER mentioned is arc blow. This is caused by magnetic field build up primarily in DC welding. After you try a few things to cure the problem, try moving the ground on the work piece. Normally, the arc will tend to blow forward away from the puddle. Sometimes this can be used to advantage in vertical
or overhead welds to better control the puddle.

[Tinbasher]

This ones wide open. What works for you? Experience, time etc. TIG. is nice buts it's slow 1/3 the heat effect zone of Oxy/Acetylene. A good structural weld. MIG is fast and I like it because it frees up one hand. I hammer weld Mig welds have done for 30 years. (Butt Welds) 1/2 the heat effect zone of Oxy/Acety. Oxy/acetylene is what I used for the first 15 years of my trade. Everything Butt Hammer welded. Easier to work the weld harder to control the heat effect. I use all three but prefer the Mig because of time and being able to work single handed.

[nick c]

I bought a new Miller 250 MIG about 21 yrs. ago and I love it. I have used .045 flux core a few times but that was only for a job with a bit of rust or it was outside the shop where I could not block the wind. The gas I used is called Argon CO2 mix, It produces a smooth weld. I have welded cast iron a few times and the weld was so hard that a milling machine with a carbide cutter would not scratch it, I had to use a grinder. The problem of a hard weld only happens on cast iron. I always use .035 wire for thick or thin metal. When I need to weld sheet metal less than 16 ga, I usually don't run a continuous bead, I turn the voltage and wire feed down and I BAP weld it. I coined this term years ago. Just pull the trigger and let off quick, move over 1/4" and repeat. I sometimes punch 3/16" holes in one of the two sheets and plug weld it, it produces a flat weld. If you have a problem blowing holes through, clamp a piece of 1/8" aluminum on the back side.
carry on nick c