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Decryption: the Rockwell index what is it for your kitchen knives?

The Rockquoi index? Granted, Rockwell sounds more like a building in Manhattan or a super badass actor. But again, we are talking about a kitchen knife and in particular the hardness of the blade, an essential criterion to consider when making a purchase.

The Rockwell index is a very practical tool for accurately determining the hardness of your knife. So that you know how to use it wisely, we decipher it for you! Let's go !


Rockwell Scale Definition

Before embarking on the analysis and reading of the Rockwell index, we must begin by defining it.

As we told you above, the Rockwell index is a tool that allows you to precisely define the hardness of a blade . This is today the classic method of measuring the resistance of a blade for a kitchen knife. It is calculated by measuring the depth of the indentation left by a heavy load on the metal of the blade.

What is the point of such an index? The latter allows cutlers to measure, control and balance 3 central factors in the manufacture of a quality product :

  • Hardness
  • Flexibility
  • Tenacity

Each kitchen knife will have its specificity and therefore a different Rockwell index which will be assigned to it, depending on whether it is a chef's knife, a paring knife or a peeler for example.

How is the Rockwell index measured?

The Rockwell index is based on a simple test: the diamond test or Rockwell hardness tests. It makes it possible to determine the resistance of a knife with regard to the depth of penetration of a diamond ball in the steel of the blade.

In order to properly perform such a test, the metal of the blade must have been heat treated, but also have a completely flat surface. If such conditions are not met, the test results may not be accurate.

Following this, the blade is struck using a diamond-tipped cone to obtain a notch, the depth of which will then be measured using a prism of a given force. The results are then used to create a scale which will compare the results on the various metals tested, and which will thus make it possible to determine the resistance of these metals in a comparative way.

What are the Rockwell indices?

The Rockwell tests make it possible to calculate the Rockwell index of a blade from among 30 available Rockwell scales. The Rockwell indices are thus, most often, represented by a scale, because the Rockwell tests only make it possible to measure the hardness of the surface of the material, even though the inside of the knife may be stronger. Because of this, manufacturers prefer to indicate a scale of numbers for their knives, which allows for a margin of error in the test results.

But what do these scales actually mean?

Attributes of knives with a high rating:

In the event that Rockwell testing gives your knife a high rating, that means your kitchen knife is formed from a hard steel. This will allow it to retain its sharpness longer.

However, if the blade proves to be too hard, it will likely break more easily . This is particularly the case for knives whose hardness score, calculated in RC, is greater than 65 RC. It should also be noted that such knives, whose steel is harder, will require more time and more effort to be sharpened. It is therefore necessary to take a knife whose rating does not exceed 60 RC .

Attributes of knives with a low rating:

Conversely, a lower hardness score below 50 RC means that the steel is too flexible , it is little or not used by the major cutlery brands, its edge will last less than knives with a higher score. students.

What is the ideal index for my Chef's knife?

The ideal steel hardness index seems to be around 58HRC. This type of steel retains the sharpness of the blades over time, and this hardness poses no problem in sharpening them easily. The Ultimate Chef's Knife has a Rockwell rating of 58 RC because we wanted to give it a razor sharp edge while making sure you won't have trouble re-sharpening it.

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