Description Designed for grinding non ferrous metals like aluminium, brass and copper. The formulation resists loading or clogging of the wheel. Depressed centre wheels may also be referred to as raised hub wheels. The depressed centre design allows the flange/lock nut to recess within the wheel so that it can be used for various grinding applications. Depressed centre wheels are designed to handle the most severe right angle grinding applications from heavy stock removal to rough blending.