Sait .045 cut-off discs, flat and depressed center. Pearl Abrasives, same thickness. If you get a die grinder, find someone who has one and try it. You'll be disgusted with three things in short order. How shitty they cut welds, how much air they use, and how much a good one costs. My air die grinder costs almost 500 dollars and it's barely adequate.
If you still insist, use only Jimmy Shine Death cut off wheels. They are the only ones that will cut worth a crap and I've tried everyone I can get my hands on.
If you want to use a corded grinder, get the Milwaukee 4.5-5". You will never wish for more power, or durability.
WARNING- DO NOT DO PUSH CUTS, AGAIN, DO NOT DO PUSH CUTS
If the sparks are not trying to catch you on fire, you are doing a push cut, do not do that.
I'll get an exact model of welding hood to get. #1 rule, buy the lens covers, buy a lot of them and keep your field of vision clear. That is the only way you can see what you are doing. I change mine at least once a week. Welders like to stick their face in the smoke and it clouds the lens that is covered in metal grit so when you wipe it off, now not only is it cloudy, it's also scratched to shit.
Grinding wheels and flap discs. Get Pearl Green Back in 40 grit. Get the 3M Cubitron hard disc with the attached 5/8-11 mount. They rule. They cut faster and longer than anything else. They make a Cubitron flap disc, sometimes they work a little better than the Green Back, sometimes they don't. You want the flap discs that are threaded, not the ones you hold on with the nut.
I'll get more later.