Scrapper of metal
I've got Norton wheels on it, both K hardnessHow much pressure are you putting on the tool? Is the wheel a good quality one? I got Norton white wheels for the 8" and I can touch up the metal lathe .040" parting blade in pretty controlled way. But those white wheels are soft and I don't think they would last long for 'general grinding' - odd jobs around the shop shaping cold-rolled steel. I kept my 6" grinder for that.
That grinder has CBN wheel which are not diamond wheels. CBN is cubic boron nitride and is the standard among turners.Don't diamond wheels need water? My flat diamond sharpening plates need water lubrication or they will load up quickly. Or are the coarser diamond wheels OK run dry?