Unsharpened diamond, square banner on the subject of Rockwell hardness of blade steel

Rockwell hardness (HRC)

The measure of all blades

Unsharpened diamond, landscape format banner on the topic of Rockwell hardness of blade steel

Rockwell hardness (HRC)

The measure of all blades

Rockwell hardness

... is an internationally used unit of measurement for the hardness of knife blades and other materials. The abbreviation is made up of HR (Hardness Rockwell) and a letter that indicates the scale and thus the exact type of test force and test specimen.

The test method is based on the penetration depth of a test specimen into the material. There are a total of 11 different test loads and test specimens. These scales bear the letters A-H, K, N and T. Knives are usually tested with the scale "C" (i.e. HRC).

We therefore concentrate on this.

HRC

A diamond cone or carbide ball is pressed into the blade with a predefined force. The penetration depth is measured and converted into a hardness value.

The higher the HRC value, the harder the blade. As our grinding units are diamond-coated on one side, the hardness of the blade is irrelevant.

50-52 HRC

Such a low hardness is usually found in cheap knives. These become blunt very quickly and are also easy to bend.

Typical steel grades:

440A (50-52 HRC): A martensitic stainless steel that is often used in kitchen knives and other inexpensive cutting tools. It offers good corrosion resistance and moderate hardness.
420HC (50-52 HRC): A martensitic stainless steel that is often used in inexpensive knives. It has good corrosion resistance.
AUS-6 (50-52 HRC): A Japanese stainless steel that is comparable to 440A. It is used in cheaper knives.
7Cr17MoV (50-52 HRC): A Chinese stainless steel that is often used in inexpensive knives. It is similar to 440A steel.
X50CrMoV15 (50-52 HRC): A European stainless steel that is often used in high-quality kitchen knives. It also offers good corrosion resistance.

53-55 HRC

Knives in this range are relatively soft. They are still easy to sharpen, but also lose their sharpness quickly and therefore need to be resharpened more frequently.

Typical steel grade:

420J2 (52-55 HRC): This is a relatively soft stainless steel that is often used for cheap kitchen knives.

55-57 HRC

This hardness is typical of many European kitchen knives. They represent a very good compromise between sharpness and durability.

Typical steel grades:

AUS-4 (55-57 HRC): A Japanese steel used for less expensive knives.
420HC (56-57 HRC): A stainless steel commonly used for pocket knives and inexpensive hunting knives.

58-60 HRC

These knives are harder and retain their sharpness longer, but are more difficult to sharpen. Many high-quality knives, especially Japanese kitchen knives, but also outdoor knives fall into this category.

Typical steel grades:

8Cr13MoV (57-59 HRC): A Chinese stainless steel often used for cheaper but high quality knives.
440C (58-60 HRC): A stainless steel with a good balance between hardness and corrosion resistance.
AUS-8 (58-60 HRC): A Japanese stainless steel suitable for a variety of applications.
VG-10 (59-60 HRC): A high-quality stainless steel from Japan that is often used for kitchen knives.
S30V (58-61 HRC): A high-quality powder metallurgy stainless steel often used for high-end knives.
CPM-154 (58-61 HRC): A powder metallurgy stainless steel with high edge retention and good corrosion resistance.

61-65 HRC

Knives in this range are very hard and retain their sharpness for a very long time, but are also more susceptible to chipping and breaking if used improperly or when cutting harder materials due to the brittle steel required for this. These knives are more suitable for specialised applications.

Typical steel grades:

D2 (60-62 HRC): Semi-stainless tool steel known for its high hardness and wear resistance.
M390 (60-62 HRC): A powder metallurgy stainless steel known for its excellent edge retention.
Elmax (60-62 HRC): A powder metallurgy stainless steel with a good balance between hardness, cutting ability and corrosion resistance.

über 65 HRC

Blades with this high hardness are rather exceptional and not common. They are extremely rigid and brittle and can hardly be ground without diamond-coated grinding units.

Typical steel grades:

ZDP-189 (64-67 HRC): A Japanese powder metallurgical steel that achieves very high degrees of hardness.
Shirogami (White Steel) (65-66 HRC): A Japanese carbon steel used for traditionally made Japanese knives.
Aogami (Blue Steel) (65-67 HRC): Another Japanese carbon steel that can achieve an even higher hardness.

Influences on blade performance

Material: The type of steel and the heat treatment influence the achievable hardness and the overall performance of the blade.

Use: Harder blades are better for fine cutting work and applications where long-term sharpness is important. Softer blades are better for applications where flexibility and ease of sharpening are critical.

Care: Harder blades require more careful care to avoid chipping and breaking, especially with harder or bony materials.

Choosing the right HRC value

Choosing the right HRC value depends on individual requirements and preferences.

For everyday use in the kitchen or for outdoor activities, an HRC value between 55 and 60 is often ideal. Professional chefs and knife enthusiasts may prefer harder blades that stay sharp longer, while casual users may favour softer and easier to maintain blades.

To summarise, Rockwell hardness is an important factor when choosing knives, as it significantly influences the sharpness, durability and maintenance properties of the blade. A balanced understanding of your own needs and the degree of hardness helps when selecting the right knife for the respective area of application.

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