grind

1. Hollow ground—A common grind where a convex hollow is removed from both sides of the edge. It produces a very sharp edge but being so thin the edge is more prone to rolling or damage than other grinds. It is unsuited to heavy chopping or cutting hard materials. Straight razors are hollow ground. This grind is used extensively in mass produced knives. 2. Flat ground—The blade tapers all the way from the spine to the edge from both sides. A lot of metal is removed from the blade and is thus more difficult to grind, one factor that limits its commercial use. It sacrifices edge durability in favor of more sharpness. The Finnish puukko is an example of a flat ground knife. A true, flat ground knife having only a single bevel is somewhat of a rarity. 3. Sabre ground—Similar to a flat ground blade except that the bevel starts at about the middle of the blade, not the spine. It produces a more lasting edge at the expense of some cutting ability and is typical of kitchen knives. 4. Chisel ground—As on a chisel, only one side is ground (often at an edge angle of about 20 – 30°) whilst the other remains flat all the way to the spine. As many Japanese culinary knives tend to be chisel ground they are often sharper than a typical double bevelled Western culinary knife. (A chisel grind has only a single edge angle. If a double bevel has the same edge angle as a chisel grind, it still has two edges and thus has twice the included angle.) Knives which are chisel ground come in left and right-handed varieties, depending upon which side is ground. 5. Double bevel or compound bevel—A back bevel, similar to a sabre or flat grind, is put on the blade behind the edge bevel (the bevel which is the foremost cutting surface). This back bevel keeps the section of blade behind the edge thinner which improves cutting ability. Being less acute at the edge than a single bevel, sharpness is sacrificed for resilience: such a grind is much less prone to chipping or rolling than a single bevel blade. In practice, double bevels are common in a variety of edge angles and back bevel angles. 6. Convex ground—Rather than tapering with straight lines to the edge, the taper is curved, though in the opposite manner to a hollow grind. Such a shape keeps a lot of metal behind the edge making for a stronger edge while still allowing a good degree of sharpness. This grind can be used on axes and is sometimes called an axe grind. As the angle of the taper is constantly changing this type of grind requires some degree of skill to reproduce on a flat stone. Convex blades usually need to be made from thicker stock than other blades. It is possible to combine grinds or produce other variations. For example, some blades may be flat ground for much of the blade but be convex ground towards the edge.