- Norton Metal Grinding Wheel - 4in. Dia. Price For: Each Item: Depressed Center Wheel Type: Type 27 Application: Ferrous Metal, Gray Iron, Stainless Abrasive Material: Aluminum Oxide Diameter: 4" Arbor Size: 5/8" Wheel Type: Cutting, Notching , Grinding Thickness: 1/8" Series: Norton Metal Max. RPM: 15, 280 Grit: 24 Grade: Extra Coarse Country of Origin (subject to change): China