I loked the spot weld cutter
The link below is from Harbor Fright and I have used these successfully they are cheap enough and if you break them it is not that big of a deal
I used a spring loaded punch to create a dimple in the spotweld Doing the pinch three or four times made a dimple enought that the wolbbling and walking was not minimal and not bad I have literally taken a whole truck cab apart with these cutters
They are double sided cutters so when one side wears out you just unscrew it and flip it over and you got a new cutter like 2 for the price of one.
Remember when cutting metal to go slow, fast cutting will ruin the cutter and going slower allows you to not cut trough the base metal.
Also one other note these cutters have a spring loaded center point that can be adjusted for more or less tension I adjusted this tension to my liking seemed to work better when it was a little stronger and I had to press on it a little more to get the cutter to the metal I tested the tension out of the drill but you can also test in the drill too much tension and it doesn't cut through well and too little and it walks away from where you want to cut.
Working with it you will find the right settings you need to remove the spot welds
I have had great luck with these cutters some of these cutters I have removed nearly 200 spot welds REMEMBER TO GO SLOW others I got maybe 60 cuts probably was me being in a hurry
I have harbor freight store close by so getting these was not a problem I would buy about 5 at a time and I would say that I have used about 15 total on my project I know that sounds like a a lot but I have literally taken 2 trucks a part to put one together Check out my build thread Major Cab Repair Maybe it will give you an idea that I have really take every spot weld out of one of these trucks
I say to each his own bit I have had great success with the spot weld cutter and I have spent about 80 bucks on them and I still have a few left for the remainder of the spot welds I need to remove (Removing the roof panel soon)
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=95343