roof skin replacement
What he said. You can get the cut off wheels themselves in different thicknesses, wider ones for grinding the spot weld, thinner ones for actual cutting. Could also source spot weld cutting bits that are without the centering pin. They are more of a traditional drillbit appearace and seem to not only last longer, but do the same job. For the actual rough cut the roof skin off, do urself a favor and use an airhammer (if available) with that chisel bit shown above. Saves alot of time and i think its easier to work with the small pieces of metal left at the pinchweld than having the entire roof to remove after its all drilled out. Personal opinion tho.