In my experience with grinding disks you get what you pay for. It's also my experience that Norton is the best disks I've ever used and most companies I've worked for, use them exclusively, but I have worked on some jobs where the contractor bought the cheapest crap they could find. But I also have to say a Norton disk is the only one I've ever saw explode but, it was not the quality of the disk that was at fault, again that is my opinion but, I saw the grinder that the disk was mounted on dropped on the ground from about 4-5 feet off the ground so I would definately say it was being dropped and probably cracked that caused the disk to explode not poor quality. A sorry a** helper dropped it and I saw it, he looked around and I acted like I didn't see it and kept working on my weld, I took for granted that the stupid a** helper surely had enough sense to take the wheel off tell the welder it had been dropped throw the wheel away and replace it with a new one, this is so basic safety it's taught from high school shop class. I was wrong, and not 5 min. later the welder had to give the helper a lesson on how to properly grind a root pass in line pipe. Well before I could holler and tell the welder to change the wheel it had been dropped, because obviously if the helper had to be shown how to grind a root he just might not have enough sense to change a grinding wheel that had been dropped but, sure enough before I could warn the other welder the grinding wheel exploded in his face tearing open a gash from the corner of his eye to the oppisite corner of his mouth barely missing his eye but really messing up his nose. Needless to say I felt awfull, of course I told the foreman what I had saw happen and the helper at fault was promptly fired as he should have been. I felt like I should have been fired with Him, but the foreman said no it was not my fault, but I sure felt like it was, and I made a vow to myself from then on I don't care if a co-worker thinks I'm a nosey busy body or if the helper would have thought I was a snitch or if I think someone has enough sense to do something, if it is safety related and can cause someone to get hurt or damage equipment I will not hesitate to tell whoever needs to be told, in this case I think lookin back it should have been the other welder. So he could have taken care of the grinder and determined how to approach the helper about his fault in the deal. Anyway I'm getting off topic but, it is my experience that nomatter what kind of equipment you decide to buy, if it can cause a potential accident if not manufactured properly or poor quality is an issue if you are in doubt about the equipment being fit for service DON'T USE IT, take it back to the store and tell them hey somethings wrong here. My 2 coppers.

Thanks for the feedback, guys.  I tried another of the TSC POS disks, and guess what?---same song, second verse.  As to the possibility of being wet--nada.  They were in a dry box.  As to whether or not it was running true--I don't know, because when the grinder tried to walk out of my hands, I shut it down PDQ.  I've seen what a radial arm saw blade does when it explodes, and it aint pretty!  Anything spinning that fast needs to run smooooth.  I didn't get this old by being stupid, so the rest of the disks are going to be consigned to duties along the line of either trot line weights or low and slow clay pigeons--anything to keep some poor schumck from getting hold of one and possibly injuring or killing himself.  (NOTE TO SELF---Stay the @#$% away from TSC!!!)