Ron if you don't want to work with lead you can call "Johnson Mfg" - http://www.johnsonmfg.com/ they have a whole line of lead free solders that will work. You have to use a different tinning and the melting temp is a closer tolerance than lead. But you can sand / DA with fear of those little lead particles... :yes:

i still dont understand exactally why some show up and some dont. i found out during my build that the lower portion of my quarters had rivets holding them on. nothing else.... there were no issues with hairline cracks visible at any point in time.

It's not the movement, it's the hardened mig weld vs the normal sheet metal. It'll expands differently with heat. And it's worse at a place like the top of the b pillar, where sun would hit in directly.

ive heard a lot of possible explanations and thats one of them. others have been filler shinkage (although some say there car sat for a year before painted) and ive also heard joint prep/design with some using a butt weld and others using a lap weld. it would be interesting to take the temp of the body panels and see if there was any real difference between parts that are doing it. i have a few areas that have been worked and mig'd back up, and im planning on doing the marker lights soon. id rather not deal with any hairline cracks.

also, why would a chunck of lead in a seam not expand any different than the surrounding sheet metal?

sorry for the hijack.....

I'd have to disagree. You're telling me that metal finished MIG wire will have significant enough difference against cold rolled steel in expanding and shrinking at temperature changes ,that it will show through primer and paint?If your theory is true, why I do not see brazed roof & quarter seam on many imports bleeding through? Does brass expand and shrink at same exact rate as steel?

I'm working on 94 Supra at the moment ,replacing one quarter,the seam was brazed with metal finished with zero filler or lead under paint,with less than 1/16" line of brass visible in the actual seam.

I work on and own MKIV Supras and have yet to see one that would show this seam through paint on these cars.

I also have done plenty of antenna,maker light,wipers and various holes shaved over last 22+ years on customer's cars with MIG and have not seen any come back .Can you explain?

How many black cars have you mig welded the top of the b pillar with a piece of sheet metal, put out in the sun and really scrutinized it looking for a line?

As far as different metal expansion rates, I don't know, I'm not a metallurgist. :)

I just know what I've seen. I see it a quite often at car shows. Even high end cars. I've actually looked at their build book, looked were they mig welded a panel on, and went to look for the line, and found it. I realize it may not have always been from the heat of the sun though.

On my Nova, someone mig welded a quarter on right under the factory seem for some reason, I cleaned it and re welded it. After the car was done and painted, out in the sun, I could see the line. Ended up putting a full quarter on it, and re-painted the whole body :( . I've seen several threads on other sites where things such as this has happened.

If you guys aren't having any come backs, more power to you. :cheers:

But I will never again put a mig weld in the middle of a panel that faces anywhere near the sky. Especially if it's a dark color. :D

Maybe it's just my luck,but I don't have that problem,lol. But if you compare lead and steel,then finished MIG weld and steel, wouldn't you think that lead would be more susceptible to temperature changes? I'm not metallurgist either but this topic has got me thinking. Honestly I just need to quit being lazy and use TIG weld butt seams just to be safe:cheers:

Brass and "bondo" don't mix.... never bondo (body filler) over a brazed area.

We quit doing that in the late 60's.

I totally disagree with any statement that the MIG weld would be somehow inferior to the TIG weld regarding shrinkage or showing seams. TIG wire is softer and is easier to control the heat on a panel - but it's not superior or inferior to a good MIG weld.

What you might be seeing is where the MIG weld is harder to grind and they've ground down the base metal too thin around the weld. The thinned metal may expand at a different rate than the thicker base metal around it. That is just bad workmanship -- but not the WELD itself. TIG is far easier to metal work... and done properly warps the panel LESS (it will be warped)... and grinds easier. Both take skill to do properly.

Greg, thanks for your input. I agree with you, properly finished MIG weld shouldn't be visible in paint.TIG weld is just easier to smooth down.

So the Lead Free Solders are better than or just as good as the Lead? Will it be equal to the show finish of Jeff's subframe work which looks very nice by the way.