[FrankR]

When I cut out the old fender arch on my car, I acccidently cut a little too much. I have welded the new arch on and most of it is fine. But there is about a 1/8 - 1/16" gap between the two panels in a couple of places. I've heard you can hold a copper plate behind it to reflect the heat and bridge the gap. I don't know where to find a copper plate. Suggestions?

[roger1]

I've heard that works well but haven't tried it.

I have had luck doing on/off/on/off with the mig trigger at about 1/2 second.

[oldred]

Really, that much gap should not be much of a problem if you take your time, Patience being the key here. It would weld quite easily with a torch if that is an option.

[MARTINSR]

You can build up weld on the edge of the metal by tapping over and over on the trigger. I have a piece of copper water pipe smashed down at one end for my "backer".

Brian

[35WINDOW]

I agree that it can be done, but as a general rule you will shrink the metal around it due to so much heat (more Bondo)-

Craig

[rrmccabe]

The reason for the copper is not to deflect the heat. Its to hold the puddle in place so it does not fall through and the weld wont stick to it.

I have done it before but dont use it in practical applications.

Rich

[oldred]

This should weld just fine without a backing if one is not available. I would use the trigger tap method, assuming MIG here. As I said before patience is the key, You can build up one side until the gap is closed or carefully bridge the gap in one spot by "tapping the trigger" and add to that. Since you need to go slow anyway to allow the metal to cool if you take the time to clip the wire each time, at least during the bridging part, you will find the process will go a lot easier.

[Kampr]

The copper also acts a sink to absorb the heat. I have used aluminum before when copper wasn't available.

Danny

[adtkart]

For a copper backer, I used a union (sleeve)for large copper tubing. Take a hacksaw and split the union and hammer it flat. As was said, you need to keep the heat down anyway. Use pliers or vice grips to hold the copper in place.