Wiki-Rough whetstone

Of the three types of whetstone, the coarsest are those used mainly in the shaping process, which is the first step in sharpening. In the case of synthetic whetstones, it often refers to those with a grit size of #320 to #800. Due to the coarseness of the grindstone, scratches on knives are deep and the grinding power is high. Therefore, it is used when the shape of a kitchen knife is greatly deformed, for example, when repairing a scratch or a distortion.