Just thought I might mention this. One must be very mindfull of welding on something that is electrically grounded. Like I have a metal workbench with a pull out vice (in 2" tubing like a trailer receiver) that I sometimes weld on because it can hold my work so nicely and at comfortable height. There are numerous outlets built into the bench. The problem is, if you loose your ground clamp on the work, a whole lot of current can go unintentionally through your electrical system ground and fry it! I often use vice grips on the work for the ground, and attach the ground clamp to the vice grips because I find the ground clamp always slips off most work!
The same unintentional ground could happen if you had a metal cased grinder or other tool lying on your work.