difficult choice for easy sharpening... what would you do ?

[dkb45]

What are the CBN rods for the sharpmaker for? I have all the others and understand their purpose. Where does the CBN fit in?

CBN and Diamond can do one thing that no other readily available abrasive medium can, and that is abrading vanadium carbide. In steels like S30V and M390 a large part of the steel is made of vanadium carbide which most abrasives cannot wear down, so they just wear the steel around the carbide down. I don't know a lot more about the physics aspect but I can say that using diamonds for sharpening makes my edges on super steels feel a lot sharper and they cut a whole lot more aggressively. I don't think I can go back to non diamond stones now, I am hooked!