automobile metal repair and panel welding

I was talking to a nice gentlemen recently who had read my rust article. He wanted to know if the guys who had redone his Camaro did it correctly. I asked him if he had any photos of the resto process. Well in fact he didn’t. But he described what he had seen when he visited the restoration process. I had a few follow up questions that he couldn’t answer, bottom line I can not stress enough how important progress photos of your restoration or car build are. Photos are the only way to document what was done to your car.
Moving forward I think this guy has some interesting questions about how to properly repair or restore the body on any car.
Let me start this explanation by saying that I was learning the body trade in the late 50s. This was an interesting time in the evolution of automotive metal work in the new car construction. Going back to the early beginning of car construction on assembly lines The sheet metal used in body panel stampings was much thicker than it is today. Since the late 20’s and early 30’s where it was not uncommon to see sheet metal on cars that was 10 and 12 gauge metal. Most body panels were 14 gauge. Connecting body panels was achieved by fixing the steel panels to a wooden body skeleton with nails and or screws. Accident damage was repaired by hammering out the dent and metal working the area until it could be filed smooth. The addition of Lead applied to the metal provided another way to smooth the panel before painting. Lead soon became an accepted repair method. Experienced leaders also became body artists in customizing metal bodies. When I came on to the car scene in the late 50’s sheet metal was much thinner so the hammer and dolly technique was an art, too much was a bad thing. Wood skeletons were gone. Body panels were welded together and exterior seams were leaded. The practice of attaching panels was being done by the form of “spot welding” Somewhere along in the late 40’s fiberglass car bodies were “experimental” In the early 50’s “Bondo” a plastic body filler was making it’s debut, and has been misused ever since.
Not to say that new technology hasn’t improved many aspect of automotive body work, but if we take a look at the old school methods we might get an understanding of what works and why. Going on the premise that back in the 50’s a body repair was done to be permanent. Today insurance companies consider an auto body repair permanent if it lasts 3.5 years. Dissimilar materials rarely stick to each other forever. Plastic body filler isn’t permanent, over time it lifts, puckers, shrinks, or peels. When was the last time you saw lead crack chip or peel on an auto repair. Enough said about smoothing body work techniques, remember “less is best.”
That brings us to the last tidbit of metal body work, or the art of welding and panel fitment or replacement. There should be no argument that the best repair to a metal car body is the exact body panel replacement attached in the exact method done by the factory. Lets say you have a rusted out quarter panel on a 1965 Mustang Coupe. In my opinion the best way to fix the rust is to remove the complete quarter panel, call the factory and order a OEM quarter panel and attached it with spot welds following the factory weld map, the roof seam gets lead and the trunk seams get a touch of sealer. Well you and I know that there are a few flaws in that procedure, primarily it is next to impossible to get OEM panels for older cars. So we are stuck with aftermarket panels that may not be the same gauge or of the same stamping quality of OEM panels. Even when working with complete aftermarket panels they can be still be attached just like the factory did it. Often we find that a lot of shops don’t have the same spot welding equipment as the factory. Consequently, other welding methods are and can be used. Bear in mind that the more heat that is applied to a metal panel the more “oxidation” occurs. Yep heat causes metal to oxidize. Isn’t the rust or “oxidation” the reason we are doing this in the first place? Remember in the welding repair process you will need to assure yourself that where heat was applied to weld the metal, you are able to clean up the metal and treat it so that the oxidation process is stopped or slowed as much as possible.
What if you have to repair metal and no complete panels are available, what then? Well this is where many opinions enter into the “what’s right, what’s wrong” arena. Many body guys think that butt welding replacement panels in is the only proper way to go. Others still use a “lap” seam to put partial panels on existing sheet metal. First let me say that butt welding eliminates the pocket between two panels that traps moisture and creates rust. But I must say it takes a very skillful welder to butt weld a big patch panel into existing sheet metal without causing a lot of distortion. The more distortion, the more body filler is needed, now you have a whole different set of problems. Remember when it comes to any filler “less is best” As an alternative is the overlay of panels, as we discussed this method put two pieces one on top of the other using a 1/2 inch lap seam. The lap seam gives moisture a place to start oxidation. If you can seal both sides of the seams you will slow the possibility of oxidation occurring. Don’t forget that the factory uses a type of “lap joint” when they spot weld panels together. When performing a lap weld on an external panels I will always sweat the seam with lead when the welding is complete. Lead goes a long way to “seal” the lap joint. Bottom line either method can work well, both methods have pluses and minuses, sometimes you just have to trust the advice of the guy doing your work. Document it with photos.
Well we have looked at spot welds and the types of welds but we haven’t discussed the type of welding equipment. Whether it is electric stick or wire feed, Mig or Tig, or gas and stick, good results can be had by any experienced welder with any choice of welding process. One thing to be mindful of in the “good old days” we worked on body panels with the “less heat” approach. Braze was one such method that used less heat than arc or gas welding. When we were finished brazing a panel it was most always smoothed with lead before painting. I don’t ever remember problems when doing this type of repair. In recent work we notice that the plastic fillers have a tendency to “lift” or separate from braze material over time. This mystery of separation, seems to be due to the flux residue in the brazing process. So don’t use plastic filler over a brazed seam or joint. If you lead the braze first then apply the plastic filler I don’t think you will have a problem with “lifting”

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5 Responses to automobile metal repair and panel welding

  1. Thanks for nice tips and ideas about welding panels. For now all my welding work is never like i want it to be. Some of notes in this article will surely help :)

    • Bruce says:

      Thanks for the kind comments! I am sure that there are many more skilled panel welders out there that I am. Many may have different advice. One thing is for sure “practice make perfect” The more you do it the more you will learn and the better you will get at it.
      It looks like you have some connection with Miller Welding Equipment. If so I am sure you are pretty good at welding. I recently visited the Miller Welding display at the Ocean City, Maryland annual car show. Miller has a lot of excellent equipment and many very experienced welders manning their booth, it was a very impressive presentation. For those of you who have not seen the latest in welding equipment a stop by a miller display at a local car show will certainly inspire you and get you pumped to replace some car panels. Thanks again for the comment.

  2. jay says:

    Awesome tips for repair retro car. the main problem is how to remove rust and then make good weld, but in your post I get best methode how to remove rust. thanks

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  4. I despise bondo, I will never use it unless I am asked to (I would never use it on my car) I think that pulling a dent out is the best way, don’t cover it up!

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