The grit of a Dayton grinder refers to the size of abrasive materials present on the grinder. A high grit size (120 etc.) denotes the presence of finer abrasives in the grinder wheel, leading to smoother surface finishes. Lower grit sizes (30, 36 etc.) represent coarser abrasives that scrape off many materials faster. Choose according to your applications for coarse or fine grinding, while keeping in view the material (workpiece) properties.