Highbeam
Super Member
Neil, I've welded 3/8" plate onto 1/8" sheet or angle and it can be done. You need lots of power but you aim the power/heat at the 3/8" material and make sure your puddle runs onto and includes some of the thin metal. After the weld, you check the backside of the thin metal to be sure you've burnt into the thin stuff and gotten enough penetration. I agree that welding plate onto sheet metal less than 1/8" thick is very tough since even the puddle burns through so easily. Exhaust tubing is a fine example of a tough weld if you are using moderate heat.