Knife Blog

In the previous blog, I wrote mainly about natural grind stones, so I will write about artificial grind stones today.
 
There are generally 3 types of grind stones:coarse-grit grind stones, medium-grit grind stones and fine-grit grind stones.
 
Grit levels depend on size of grind stones’ grains. Coarse-grit grind stones are used when sharpening of knives is started or when saw-edged knives are fixed. Medium-grit grind stones can remove streak of coarse-grit grind stones, fine down to and fair blade edges. Thus far, 80-90% of the whole process of sharpening is completed. Finally, fine-grit grind stones can remove streak of medium-grit grind stones and fair blade like a mirror. Fine-grit grind stones can make knives sharp for longer time.
 
Every grind stone has every number. Briefly, the number of coarse-grit grind stones is smaller than 400. The number of fine-grit grinding stones is larger than 3000. Then, the number of medium-grit grind stones is from 400 to 3000. If the number is larger than 8000, it is sometimes called super-finishing grind stones.
 
Generally, hard grind stones are good for carbon steel knives and soft grind stones are good for stainless steel knives. However, soft grind stones can be good for extremely hard knives, such as powder high‐speed steel knives.
 
Artificial grind stone are made by kneading and burning. Most coarse-grit grind stones are made by burning and most fine-grit grind stones are made by kneading. Grind stones made by burning have to be immersed under water by the time bubbles from grind stones stop. On the other hand, grind stones made by kneading don’t have to be immersed under water. The way of distinguishing grind stones made by burning and those made by kneading is if grind stones froth under water or not.
 
One of the most important cares of grind stones is to keep them flat. The more often grind stones are used, the more the center of them wears down and the higher the edges of them are. Under such a condition, we cannot sharpen knives very well, so we have to flat the surface of grind stones by flattening stones.
 
*On the picture, the whetstone on the left is coarse-grit, the one in the middle is medium-grit, and the one on the right is fine-grit.