47-59 Spot Welder Help

[1project2many]

I will be replacing some panels in a "not of this forum" vehicle and I suspect one or two folks here have experience with single side spot welders. I have an old spot welder similar to a Marquis Redi-Spot. It uses a gun very much like this one:



I would like to select the most appropriate rod to try with this welder. I cannot find a manual for this tool but it used to use special "copper coated" welding rods. I have found an article for a "DIY Spot Weld Gun" which noted the large copper outside ring on the gun acts as a heat sink so standard arc welding rod works fine. I have found posts on welding threads where folks say this welder should use "carbon-arc" rods. Carbon-arc welding by the looks is essentially creating an electric torch to weld with. Maybe not the best for spot welding? Finally, I can find copper allow rods designed for pressure spot welding. These rods pass current through the parts being welded to "resistance weld" the panels at the weld point. Unlike the other two solutions, this method does not arc weld the panels. It spot welds.

So... anyone have experience with this or have suggestions about what rod is best?

Thanks