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It seems there are a few of us working on floor pans or other welding challenges I have had replacing the long fronts in my 67 Mustang is getting the seams to together, as well as occasional blow through when encountering thin metal or wider gaps than planned.

Copper/magnetic heat sinks in a restoration catalog that will prevent molten metal from dripping or blowing through the project which normally will prevent this, so I gave it a try. This gadget is not too expensive and it works ok, if both edges of your project are flush or flat. If not, there is too much gap between the work and the copper to be effective and it can make things worse.

I gave this some thought and expanded on the magnetic heat sink idea. I went to the local home supply store and picked up a short piece of 1”X 1/4” flat bar, a piece of ¾”X 6” copper pipe, some #6 X ¾ machine screws and nuts, and a couple of #10 fender washers.


Back in the shop, I first flattened the copper pipe in a vice to keep it uniform and flat, then I banged it a few times with a ball peen hammer to flatten the edges. I cut my flat bar to a six inch length, then scribed a line down the center, and marked to hole locations one inch from each end. I punched the holes then drilled a hole in each end. I then ran a #6 screw into each hole, and tacked if from the head to the flat bar with the MIG.




I then transferred the locations of the screws over to the centerline of the flattened copper, and drilled a corresponding hole into each end of the copper. Once all drilled and welded, I slipped the copper over the two studs. The ¾ copper flattens nicely to a bit more than 1”, giving the flat bar a nice edge.


Once the copper sink and backer are fab'ed together, I went to the seam in the floor pan (transmission tunnel) line and laid the sink up next to the area I wanted to pull together, and marked the bolt holes with a sharpie. I then drilled a 9/64 hole just below the seam in the good floor pan material. From under the car, I pushed the two studs through the holes, and then from inside the car I placed a fender washer and nut on each stud, and ran them down snug until the seam was pulled flat and the copper was snug up against the metal.




Then it was just a matter of tacking and welding the seam closed. When done, unscrew the nuts; drop it out, weld up the holes and your done.





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That is a AWESOME TIP!!!!! Wish I knew that before I did my floor pans. That would have made my job turn out so much better. Live and learn. If anyone is doing this task on there cars, this will help make your job come out so much better than a lap job.

Sweet Tip. I will use that for the quarters!!

Thanks very much.
 

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I used a similar method to this when i did the floors in my mustang. As long as you can keep the copper pressed tightly to the metal your welding, it works pretty decently. Also nice write-up.
 

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Discussion Starter #4
Yep, screwing it tight to the work with the studs and nuts works a lot better than yelling at the wife to "close your eyes, and dont worry about the burns".
Thanks
 

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If you don't happen to have any copper handy you can use aluminum bar stock the same way. I also made a cheep pannel clamp by taking a 6"X1"X1/4" piece of aluminum, slotting the center of each end about 1/2" and pinning a thin copper plate through each slot. I attached a threaded rod to the top of the copper and slipped it through a section of 1"X1" square tubing with a wing nut on the top.
This way you just slide the copper strips up between the two parts you are trying to butt weld, slide the threaded rod on the the copper and through the square tubing and tighten the wing nuts. You have a backup for the weld and you dont have any holes to fill afterward.

Scott...
 

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Discussion Starter #7
Hi Dennis, I have more Home Depot and Lowes within spitting Dist than scrap yards. I wanted an electrical break bar, but they are pricey new.
Thanks for the help with the posts. Greatly appreciated.
 

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good tip.I usually overlap the seams as that is how the factory does the floors.if you over lap you only have to drill some 1/4 in holes along the edge of the metal and do what they call plug welding and fill the holes with the welder then you seam seal both sides after.less warpage when you have less welds cause continuous welding can and most likely will give you some warpage.the factotry floors are only spot welded every few inches along the seam then sealer is used.also alot less grinding as you only have to grind down the plug welds and not entire weld along the floor seam. The cooper backing has been around yes and why the sell them,yours is a good homemade DIY tool .i only do the continuos welding on exterior panels cause you can't use seam sealer and bondo is not a sealer.
 
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