The Thin Grounding of Knives

In order to cut optimally, knives need to be ground thin from time to time. The blade of the knife is shaped to minimize resistance during cutting. Learn all about the thin grounding of knives here.

Why should Knives be ground thin?

Two things happen during cutting:

1: The object you are cutting is sliced by the sharp cutting edge of the knife. A sharp cutting edge is needed for this. You get it by grinding the knife very finely.

2: The moment you penetrate deeper into the object with the knife, the material on the side of the knife blade is compressed. Space must be created for the knife.

To ensure that as little material as necessary is pushed away, the knife blade must be as thin as possible. Then the resistance is minimal. This is achieved by grinding the blade thin.

It is often helpful to grind new knives thin. Many manufacturers do not grind their knives very thin. Even with knives that have been sharpened a few times, it is worthwhile to grind them thin. Because knife blades are usually conical, the cutting edge becomes a little thicker with each sharpening.

Drawing 1 in the above figure shows a common cross-section of a knife. The blade tapers slightly and becomes thinner towards the cutting edge. Then a cutting edge is ground at an angle of 40 degrees on the blade.

Drawing 2 shows the cross-section of a thinly ground knife. By grinding away a small piece on both sides of the knife, the knife encounters less resistance, especially with harder objects. The angle of the cutting edge remains unchanged. This hardly changes the strength of the knife.

A knife is therefore not ground thin over the entire blade, but only directly over the cutting edge.

This is how a Knife is ground thin:

When grinding knives thin, a relatively large amount of material is removed. Therefore, not all grinding methods are suitable. Below you will find information on three common practices.

1: On a coarse Grindstone

The knife is ground at a smaller angle than usual. After it has been ground thin, the knife can be resharpened on a finer stone. This will remove scratches caused by the coarse stone and form a new cutting edge.

Of course, the question arises: which grit size is best?

We recommend a stone with a grit size of about 220. A stone with a coarse grit (low number) removes material faster, but also leaves deeper scratches. With a stone with a grit size of 220, the initial thin grinding is relatively time-consuming. However, it is well suited for the subsequent regular care of your knives.

2: With the aid of an electrically driven Grinding Belt.

Knives can be ground thinly on an electrically driven grinding belt. However, such grinding machines are often not available.

The best machines are those that allow you to grind on the part of the belt that is between the drive rollers. This area can be slightly bent, which gives a better result. For grinding on the roller, it must have a relatively large diameter. Ideally, it should be covered with a slightly springy layer.

When grinding electrically, make sure that the blade is not overheated. When the temperature rises to around 200 degrees, the knife becomes softer. This can happen in small places faster than you might think.

3: With a slowly rotating Whetstone

A slowly rotating whetstone (ideally placed in a container with water) also offers the possibility to grind out knives thinly. However, it is very difficult to achieve a good result with this method. This is especially true when grinding on the curved side of the stone. Grinding is easier with the side of the stone.