This superior performance product has the highest wheel life, and combines an exceptionally fast cut rate with burn free grinding. 3X wheels are excellent for grinding plane blades, chisels, and turning tools on a bench or pedestal grinder. They handle all the hard, tough, and difficult to grind tool steels which are used for most premium plane blades, including A2. I-Grade and K-Grade Ratings - I-Grade Wheels: A bit softer, more friable, and run cooler.