Extremely coarse grits are used on very dull knives and tools. The purpose of this grit is to remove metal as fast as possible. On a very dull edge, using the most coarse grit possible will save time and will also save your finer grits from wear.
Grit: 150 and Coarser Grit
Particle Size: Over 100 Micron
Sharpening Stone Grit Chart
For those seeking an extremely high quality sharpening surface, the Shapton GlassStones meet the needs of even the most discerning sharpener....