The grit number tells you how coarse the wheel is. Most bench grinders come with two wheels. A 36-grit wheel is designed for rapid material removal. A 60-grit wheel is for general-purpose shaping and sharpening. A 100-grit wheel is for fine sharpening. A 150-grit and higher wheel is for polishing. ; Grinding wheels come in different materials, too. Standard wheels are often aluminium oxide or silicon carbide. White wheels, a type of aluminium oxide, are usually used on slow-speed bench grinders. Diamond wheels are used for sharpening very hard materials, such as cutting tools with carbide tips.