/diy/ - Do It Yourself

I've got an old angle sander. The manual says it takes 7 or 9 inch discs and it spins at 6,000 RPM. A friend has what looks to be the exact same tool except he says it's a grinder. It has a different shroud around the disk but is basically the same from there on back. Same manufacturer. I checked the arbors, the same. Motor ratings, the same. His data plate is fucked so I can't read what it spins at. My buddy says I shouldn't use grinding discs on my machine because it spins too fast. Most discs I see say they can handle 6k RPM. Some go over 20k. Is he full of shit? I think they basically made the same tool and just had different shrouds for the different roles.