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Blade

Blade Geometry, Profile and Finish

When steel is like the engine of a car, blade geometry (blade in a section cut) and profile (blade shape, especially on cutting edge) are like the chassis. A car with a powerful engine won’t be very fast with a bulky chassis and poor aerodynamics. Likewise, a knife with great steel won’t cut well with a poor blade geometry and profile.

 

Although the geometry generally does not have a major impact on the objectively measured sharpness on commonly used sharpness measuring devices, it has a profound subjective impact on the cutting feeling. The cutting feeling describes the ease at which the blade moves through food and the power needed to execute a cut.

Besides geometry, the following factors have an impact on the cutting feeling:

  • Sharpness of the cutting edge       (explained in next chapter)

  • The surface finishing of the blade  (explained later in this chapter)

When talking about a good geometry for a knife blade, one has to keep in mind two simple rules:

  • Food releases off a curved surface better than it does off a flat surface

  • The thinner the knife, the easier it moves through what it is cutting

How to produce a knife blade from a strip of steel from a steel mill?

 

Blades are punched or cut into the desired shape from pre-cut rectangular blanks of steel or directly from large coils of steel. In a cross section, the blank has a longish, rectangular profile, with a thickness of 2-5 mm and a height of 20-100 mm. The rectangular profile has to be ground to one with a sharp tip that will become the cutting edge, by removing material from the sides of the blade, through (semi-) automatic machine grinders or manually with grinding wheels or belts (see pict. blade grinding).

 

Due to grinding, the thickness usually decreases towards the tip of the blade, called distal tapering. With reduced material thickness towards the tip, the flexibility of the blade increases. Some flex on the tip is a feature needed for some cutting techniques (see pict. distal tapering).

Graphics of how a knife blade is ground from a rectangular sheet of metal into a tapered profile

blade grinding

Graphis of how a strip of steel is tapered towards the tip by grinding called distal taper

distal tapering

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