I don't run a guard on any of my grinders as they get in the way. Have had many zip cuts blow apart over the years. Never been a problem other than ruining a perfectly good disk (however I DO wear a face shield when using them). However, in this case, I was at a neighbours [lace helping hi install a set of sprayer booms that he purchased from me. The ease on one of the rams would not fit and the mounting pedestals needed to be ground a bit. He suggested just grinding the ram eye but I suggested grinding the mount instead so should the ram fail and need replacing, the replacement would slip right in. He went to his shop and came back with an angle grinder with about an 8" zip cut disc (on a 5" grinder) as it was the only disc he had big enough to read into where the grinding needed to take place. When I saw that I thought "that looks like an accident waiting to happen" and said "I'll do it" since I have had a LOT of experience with zip cuts. Of course, zip cuts are NOT made to grind on the flat but to cut on the edge (and they don't grind well at all anyways) AND I knew that that 8" disk was NOT made to run at the RPM that a 5" grinder runs at. I started to grind, feathering the trigger to keep the RPM down and to putting much pressure on the disk. Took a LONG time to get much grinding done (didn't need to take much off anyways). Last try-fit suggested that I only needed to remove a few thou to get a fit so went back to it. I must have lost patience because I started to keep the power on a bit longer allowing the disk to gain RPM. As I took the grinder away from the work, I inadvertently kept my finger on the trigger and as soon as the disk cleared the work and came to full RPM, the disk shattered. If I was alone, I would have bled out in just a few minutes. Even if I was wearing high cuff welding gloves it would have likely prevented the damage. As it was, since I was not at home I was not even wearing my usual face shield. Plat stupid games, win stupid prizes. That was a year ago last Oct (so about a year and a half ago). Still have no feeling in the outside of my left hand. If it had been my right hand, THAT would have been a REAL problem. I consider myself VERY lucky.