What is CBN (Cubic Boron Nitride)? CBN abrasive is a similar product to synthetic industrial diamonds. CBN is composed of nitrogen and boron as very very hard crystals – second in hardness only to diamond. A single layer of CBN grit on the surface of a metal wheel can grind the hardest steel and last for many years. Our electroplated CBN grinding wheels are machined from solid steel, electroplated with a layer of CBN grit and nickel plated. A CBN wheel is far better suited for sharpening high speed steels and will withstand the friction from grinding with much less heat produced than with a diamond wheel. A Hare & Forbes special-order spare part, available to order through Alltools Geelong (order code D0705) for collection in store.