knife sharpening

     

Knives are sharpene by grinding against a hard rough surface, typically stone, or a soft surface with hard particles, such as sandpaper. For finer sharpening, a leather razor strap, or strop, is often used. The smaller the angle between the blade and stone, the sharper the knife will be, but the less side force is needed to bend the edge over or chip it off. Very sharp knives sharpen at about 10 degrees (which implies that the knife's edge is a 20-degree angle). Typical knives are sharpened at 15 degrees. Knives that require a tough edge (such as those that chop) sharpen at 20 degrees or more. For an extremely durable edge (such as a chisel or drawknife), blades can be sharpened to 30 degrees. In general, the harder the material to be cut the higher the angle of the edge. The composition of the stone affects the sharpness of the blade (finer grain produces sharper blades), as does the composition of the blade (some metals take and keep an edge better than others).