Norton Medium India Bench Oil Stone #54461 The Norton MB83 India Medium-grit replacement oilstone for the IM313 sharpening system is made of 320-grit aluminum oxide, suitable for sharpening and maintaining steel cutting edges It produces durable, smooth-cutting edges and is preferred for close tolerances. The stone is prefilled with oil to save time and eliminate the need to presoak it prior to use The oil prevents metal from bonding with the abrasive surface by flushing away dislodged abrasive and metal chips This oilstone is commonly used to replace a stone in the Norton IM313 sharpening system or as a bench stone, to restore cutting edges on straight-edged tools such as chisels, knives, plane blades and precision instruments This aluminum oxide stone has a tough fracture- and wear-resistant grit that is more durable than silicon carbide and capable of sharpening to very close tolerances