I used a thin disk on a 4-1/2" angle grinder to cut it. I had to make sure ALL the fuel and vapors were out before welding it; it was a bit of a process. First I emptied all the fuel and sprayed compressed air through it. Then I let the tank sit in the sunlight for an hour or in the shop overnight to evaporate most of the leftovers. There was usually still about half a teaspoon of fuel left in it at this point so I would shake it up good and hold a long nose lighter to the cap :eek1 and wait for it to go WHOOOOSH. I would repeat the shaking and lighting until it would no longer light. It was usually ready for welding at this point, but I still needed to make sure the tank cap opening was not pointed at me when I started welding. Fun stuff.