All Tormek grindstones have been developed to optimize the combination of abrasive hardness, shape and grain size to work efficiently at the Tormek system’s low RPM.
The Tormek Blackstone and the Tormek Original Grindstone has the same grit size 220, but the composition and hardness of the grains differ, making the Blackstone better suitable for sharpening HSS and other alloyed steels. Its faster material removal is an advantage especially when shaping tools with a large bevel surface, where the grinding pressure is limited, for example, planer blades and woodturning skews. Note, you do not get a faster steel removal on ordinary carbon steel compared to the Tormek Original Grindstone.
The Original Grindstone is the best all round choice when you want both efficient steel removal and fine finish in the same stone over a wide variety of materials, from carbon steel to high speed steel.