This afternoon I used my new welder to repair some holes in the body sheetmetal. Welding closed holes is a good place to start to get a feel for welding sheetmetal, because it basically consists of blobbing into and over the hole a lot of welding wire and then cleaning up the mess later with a grinder. If you blow through the sheetmetal, which is easy before you get some experience with setting the voltage and feed-rate to appropriate levels, well then you’ve just got another hole to patch. Also, fixing small holes in the body doesn’t really constitute making structural repairs, so it is okay if the weld penetration isn’t great. For sheetmetal I use the thinnest welding wire I can (.023″) in order to keep the voltage as low as possible.
So after practicing on a lot of 1/8″ steel stock I bought at the hardware store I jumped right in to making repairs in the body. The roadster sheetmetal is very thin, so it is easy to get the weld to hot and melt right through. Trial and error with the voltage set-up allowed me to minimize this. Also, I found it necessary to back up the sheetmetal with a steel plate to effectively thicken the area and allow for better heat dispersion. Finally, I welded in very short bursts, essentially just making a long series of spot welds, which prevented too much heat build-up.
On the driver’s side floorboard there was a small rust-through that I cleaned up using an abrasive wheel. To prevent welding over rust, I used rust-converter on the hole and the area around it. To get a clean weld it is imperative that the metal be completely clean and rust-free.
I wore my auto-darkening helmet, welding gloves, and protective clothing before welding. By making each tack slightly longer in duration (by holding the trigger down sequentially longer each time) I found that he material I had previously deposited would melt into the new tack, creating one single weld-pool and allowing me to control the shape of the repair better.
In the trunk there was a hole by the jack bracket. I used a wire wheel to remove the paint from around the area and did the same on the underside of the body. I started welding up the hole from the bottom, building up tacks from the sheet metal rim around the hole inwards towards the middle of the hole, where tacks from either edge of the whole met.
After building up a lot of welding wire I moved to the inside of the trunk and built up some tacks on that side.
Then I used my Dremmel with a pair of small cut-off disks mounted in tandem to grind down the welding blobs I had created to smooth out the metal.
I quickly realized that the body that I had painstakingly washed so many times was getting covered in grinding dust!