In addition to the shape and the blade material used, the sharpening of a blade determines the characteristics of a knife. The choice of blade sharpening has a decisive influence on its suitability for specific applications. Therefore, we would like to present and explain the most common variants to you here. The different blade grindings were influenced by the typical agricultural, traditional and handicraft traditions of their regions of origin. In principle, every cut is suitable for every permissible cutting task, i.e. cutting soft to hard material. For specialized applications or materials, however, some cuts have special advantages. There is a large number of blade grindings that cannot be clearly assigned to a particular scheme. The following list of blade shapes therefore does not claim to be exhaustive. In order to explain the different grindings of a knife, we always look at the blade in cross-section. In almost every product text there are knife specific technical terms which are not necessarily known to the non-specialist. For this reason we have compiled a small guide here.
Flat grinding (wedge grinding) is widely used and has a V-shaped cross-section. The blade tapers towards the cutting edge on both sides in straight surfaces. The ratio between blade width and blade thickness determines the stability of the blade during flat grinding. As a rule, the blade thickness is again set off at a slightly steeper angle from the lateral facets in order to facilitate and accelerate re-sharpening. The flat grinding has good cutting properties due to the low material displacement of the material to be cut. It represents a compromise between the thinner hollow grinding and the more stable crowned grinding and is therefore a good all-round blade for all kinds of utility knives.
In hollow grinding (concave grinding), the blade is curved inwards towards the cutting edge. The result is a narrow, extremely sharp cutting edge which tapers at an acute angle and which, thanks to its high cutting ability, is particularly impressive for thin materials. The thin cutting edge initially means that less material has to be displaced. With deeper cuts, the hollow grinding tends to jam in the cut material due to the relatively wide blade back. Hollow grinding is relatively easy to resharpen as the cutting edge does not initially become much thicker. The disadvantage of hollow grinding is its low stability compared to flat grinding or crowned grinding, which is due to the thin material thickness in the cutting edge. Hollow grinding is popular for forged razors, but is also used for pocket knives and hunting knives.
Spherical grinding (convex grinding)
The convex grinding is also referred to as convex grinding and is curved outwards towards the cutting edge. Due to its high stability, the convex cut is primarily used for outdoor and survival knives as well as hatchets and axes where the emphasis is on chopping and lever action. As the cutting edge does not consist of surfaces as with the other grindings but of two opposite radii, the blade must be sharpened on an elastic carrier material such as a grinding belt or sandpaper with a soft backing.
The Scandi grinding describes a flat grinding that only starts at approx. 50 % to 75 % of the blade height and converges from the full width in the bevel without any further chamfer. It thus combines an extremely sharp cutting edge with high blade stability. Thus, the Scandi-Grind is excellently suited for carving fresh and dry wood, for feathering sticks and similar Bushcraft techniques. This is why it is particularly suitable for hunting and outdoor knives of Scandinavian design. The Scandi grinding is easy to resharpen on a straight bench grindstone, as the entire surface is simply laid on and the angle can be easily maintained.
In Europe, single-sided grinding (chisel grinding) has always been used for hand tools for wood and leather processing as well as gardening knives and peeling irons. It is mainly used when thin chips have to be removed from the material to be cut or when very precise work is required. One side of the blade is ground flat or minimally hollow, the other side is equipped with an angled flat grinding. In Japan the Kiridashi has been widely used for centuries and also in the West the traditional knife is becoming more and more popular as an everyday and outdoor knife due to its compact size. An advantage of this sharpening is the simple one-sided sharpening. It also enables precise cutting of wood or raw fish, such as when preparing sushi. For right- and left-handed people, the following grindings are available from different sides.