Diamond is one of the hardest materials in the world. There are couple things harder than that, such as Beta Carbon Nitride β-C3N4 or Ultra-hard Fullerite C60, but that's rather exotic science for now that anything practical. Anyway, as superhard element, Diamond crystals work very well as abrasives. You can sharpen even ceramic blades with Diamond sharpeners. Overall, diamonds have their advantages. They cut fast, they cut everything, except I guess for the β-C3N4, but there are no knives made out of it. Diamond sharpeners also last very long, granted one uses them properly, which is pretty simple, use the light pressure to prevent diamond crystals breaking out of the matrix.
All of my diamond stones are DMT at this moment. Produced by Diamond Machining Technology Inc. Including various grit benchstones, folding and serration sharpeners. I use them mostly for initial edge formation. DMTs work very well for any type of steel, and works for ceramic knives as well. Water does help when using DMT stones, it prevents the stone from clogging with metal particles. Another very important detail to keep in mind is to use minimal pressure during sharpening, otherwise you'll break diamonds crystals out of the base.
I have to note that DMT is not the only manufacturer of the diamond sharpeners. More and more companies are producing them. Spyderco, for example started making diamond sharpening rods for their Spyderco Sharpmaker 204 system. Eze-Lap is another big name in the industry. Japanese companies also make diamond sharpening stones.
Last updated - 09/01/11