Used for sharpening tools. Although natural stones, such as Washita or Arkansas, can be bought, the artificial stones such as India, Carborundum and Alox-ite are more easily obtainable and have the advantage of constant quality. There are three grades of oilstone – coarse, medium and fine. A coarse stone is used for removing a chipped cutting edge. Medium-grade stone for the intermediate sharpening stage and a fine-grade stone for the final cutting edge .