In daily use, kitchen knives and sharp blades are constantly pushed to their limits. And after frequent and intensive use, even the sharpest knife will become dull at some point. A question that every enthusiastic home cook asks himself sooner or later is: "What is the right sharpening angle for my knives? How important is it really to grind at exactly the same angle?
What is the difference between a grinding and sharpening angle?
Almost all knives (except some Japanese knives) are ground on the blade from both sides. On one side, for example, this may be 15 degrees. This angle on one side of the blade is called the grinding angle. If you then combine the two grinding angles, in our case 15 degrees x 2, you will get the the cutting or sharpening angle of total 30 degrees.
Deviations of the grinding angle
In times of CNC milling machines and laser technology, you might expect all knives to be identical. The reality is a little different. For example, individual parts of a knife are manufactured by machine, but the final assembly is usually done by hand. The same applies to the sharpening process, this is done by hand on a fine grinding belt by most knife makers.
That means that the person doing the grinding uses his hand to determine the angle. A skilled person can make the angle well even, but you really can't blame anyone for a fluctuation between 19° and 22°. The grinding angle that is measured is therefore also only a guided value. A given value of 20° may well mean that the knife you get is ground at an angle of about 18°-22°.
Which grinding angle fits which knife?
The grinding angle influences the sharpness and cutting ability of the blade. A general rule that should be considered is: the smaller the grinding angle is, the sharper the edge is, but the faster it becomes dull. The wider the grinding angle, the less good the basic sharpness of the edge is, but the longer it stays sharp.
You may already have guessed that there is no ideal knife that can do everything, but there are many good knives that can do individual things particularly well. The goal is to find the best compromise for the individual cutting tasks and to have different knives ready for very different cutting tasks.
The Scandinavian grind owes its name to its origin. It is often used on knives that originate from Scandinavia. With a Scandi grind, about two-thirds of the blade of the knife remains in its original material thickness. The last third of the blade is ground down on both sides so that the tip of the blade forms a wedge. The tip of the blade is ground down to zero degrees.
On a scandi grind knife, the wedge shape displaces quite a bit of material. The blade grind/bevel ensures that the knife produces a cleaving rather than a slicing action when in use. The relatively short blade point creates quite a bit of resistance. The pointed and straight-lined lead makes knives with such a grind perfect tools in woodworking. The straight inlet of the blade, which moves towards the tip, makes it easy to apply to the object. You can shape the wood very quickly with a targeted movement. The pointed inlet of the blade allows it to penetrate the wood very easily. For this reason, the blades of carving knives and outdoor knives are very often ground with the Scandi grind.
The disadvantage of the Scandi grind is the resharpening. Due to the straight-line grind, the entire surface of the knife must be passed over the grindstone. This process causes a relatively large amount of material to be removed. The Scandi grind is an interesting alternative to the Central European grinds due to its high material thickness, the strong splitting effect and the easy guiding during use.
A flat grind is a simple grinding. The blade is ground from the back at a constant angle on both sides. The blade is sharpened from the back at a constant angle on both sides. The pointed grind gives the knife a special sharpness.
The flat grind is used on almost all knives in daily use because of its good combination of sharpness and stability. This grind is a short bevel. This means that the blade is only ground over a small width. This brings enormous advantages, especially when resharpening. Due to the short ground section, only a little material has to be removed during resharpening in order to give the knife back its usual sharpness. The cutting angle can be easily changed during resharpening with the flat ship - thanks to the low abrasion. Similar to the Scandi grind, the flat grind has a splitting effect. Due to the length of the bevel, friction occurs along the entire length of the blade during cutting, which slows down the knife during cutting.
The hollow grind, as the name suggests, hollows out the blade. This means that the blade is ground out concavely from both sides. Due to the inwardly curved blade grind and the pointed feed to the cutting edge, knives with this grind achieve a special sharpness. At the same time, however, they unfortunately lose stability due to the extreme curvature. For this reason, the hollow grind is very often used for knives that require a special sharpness, but work with a very low resistance. The classic example of the application of the hollow grind are razor blades. However, hollow grinding is also used outside of razor blades. A knife with a hollow grind can be especially helpful for thin cut material. The thin cutting surface and sharpness of the blade ensure easy cutting of cut material. When using a knife with a hollow grind, you must be careful to apply constant pressure to the blade. Otherwise, the knife could jam during cutting. The curved grinding leads to reduced stability. The blade is very vulnerable on knives with a hollow grind. Compared to the other types of bevel, it can bend quickly
The convex grind is the most stable form among the different types of grinds. The outwardly curved blade makes the knife particularly stable. The blade is convex to the cutting edge and reduces the cutting ability of the bevel. The crowned edge is used for knives intended for cutting hard pieces like bones, carcasses or tough skins. Therefore, the crowned bevel is mostly used on butcher knives. The knives cut through bones and stubborn sinews with ease. The crowned edge can also be found on outdoor knives. In addition, the crowned edge is also used for axes and tusks due to its stability and high splitting power. Regrinding a crowned knife is comparatively difficult. This is due to the outward curved shape of the blade. With the other types of grind, the blade runs inward toward the cutting edge, making resharpening easier.
With crowned knives, the principle is that you need to resharpen them very early. Early resharpening prevents wear marks. These make regrinding more difficult without being very time-consuming. You can use different methods for resharpening a crowned knife.
The one-sided grind is used primarily on Japanese knives. Japanese kitchen knives have been ground on one side for centuries. The one-sided knife grind allows for very precise work. This allows for centimeter-precise portioning of ingredients when cooking. With the one sided grind, the blade is ground on one side. The blunt side remains in its perfect material thickness. Due to this grind, the blade is very stable. One advantage is that you can grind the blade very steeply.
A knife with a one-sided grind is superior to a flat-ground knife. This is because the cutting ability is much higher. However, the blade is not as thin as with a hollow grind. When using a knife with a single-edged blade, you must bear in mind that left-handed and right-handed people use such a knife differently. Knives for left-handers must therefore be ground on the reverse side, i.e. exactly the other way round than for a right-handed person. Regrinding the blade of knives with a one sided grind is possible without any problems. Due to the one-sided grind, resharpening is possible with very little effort.