Knife sharpening stones: grit
The most important parameter of sharpening stones is the grit or, simply put, the roughness of their surface. The difficulty is that there are several different grading systems used around the world to estimate the grit level of abrasives. The most common is gradation of grit according to the number of abrasive grains per square centimeter, which is used for synthetic abrasives. In this case, the grit will be a numerical value, for instance 600 grit (rougher) or 1200 grit (less rough). Another method of evaluating the grit of grinding abrasives uses the parameters "Extra Fine" (very fine), "Fine" (fine), "Coarse" (coarse) and "Extra Coarse" (very coarse), but their understanding may differ from manufacturer to manufacturer. Verbal indications of grit size can be supplemented by the parameter of the number of grains per square centimeter, but there is no unified standard ratio for them either. Some manufacturers of knife sharpening tools indicate the grit in microns, which is the most correct method, because the ratio of the grit of steel to the sharpening stone gives an idea of what happens to the structure of the metal during sharpening. There are special comparison tables of the ratio of grit markings in different designation systems.