If you are keen on knife specifications, you must have seen a number with RC or HRC after or before it, for example, 54 HRC or RC60. The numbers represent the Rockwell rating, a scale used to determine the hardness of a material.

HRC or RC is the abbreviation for Rockwell Hardness Scale. So, what is the Rockwell Hardness Scale? The Rockwell Hardness Scale is a technique to measure the hardness of the steel used to make knives.

There are different Rockwell scales because steel is used for many uses. In the knife-making industry, the hardness of the blades is measured following Rockwell Scale C, abbreviated as HRC or RC.

Understanding the hardness variations is crucial when purchasing knives. Read on to understand the Rockwell Hardness Scale for knives and in what way it affects the performance of the knife.

What Is The Rockwell Hardness Scale For Knives?

The Rockwell hardness of knife steel determines how strong or hard the steel is. The rating shows how resistant the blade is to permanent deformation or penetration by another material. This information may correlate to the tensile strength, wear resistance and ductility of the steel.

The higher the number on the Rockwell Hardness Scale, the harder the steel, and the lower the Rockwell scale, the softer the steel. However, this does not mean steel with high HRC ratings makes high-quality knives. 

The rating of softer steel range between 45-54 HRC, while harder steel ranges above 55 HRC. Rockwell hardness is important in the quality control of steel and the selection of steel to be used in different kinds of knives.

How is the Rockwell Hardness Scale measured?

A tipped diamond which serves as an indenter is used to measure the hardness of steel because it falls under Scale C. Here is how the test calculates the hardness of steel:

  • The steel is placed under an indenter with a starting force of 10 KGF. The depth caused by this force is recorded as the first reference.
  • A force of 140 KGF is applied for a specified period, and the depth caused is recorded. Note that the first force is not removed as they apply the second force.
  • The second force is removed, and the permanent depth is measured and recorded as the second reference point.
  • The depth between the 10 KGF and the 140 KGF is the HRC rating of the steel.

The test process is not as simple as we made it sound because it involves the use of machines and complicated math calculations. But in simple terms, the Rockwell hardness scale is determined by measuring the permanent depth caused by a 150 KGF indenter on steel.

What Does The Rockwell Hardness Scale Mean For Knives?

The hardness of steel determines the edge retention, ease of sharpening, and toughness of steel, which are major properties in determining the quality of knife blades. Here is how Rockwell’s Hardness rating affects the properties of steel.

Edge Retention

The edge retention of steel is directly proportional to the Rockwell rating. Therefore, the higher the Rockwell rating, the higher the edge retention. Knife blades made from hard steel hold a sharp edge for a long time, so you will not be required to sharpen your knives frequently.

Ease Of Sharpening

Steel with high HRC ratings is hard and, therefore, very challenging to sharpen because they have high wear resistance properties. Getting a razor-sharp edge will take a lot of time and energy.

Experts recommend that you hone your knives frequently, so they do not become dull quickly. However, if you do not have knife sharpening skills, consider blades with a lower Rockwell rating.

Toughness

Steels with a high Rockwell hardness like Maxamet are brittle, meaning that they chip and break easily when exposed to impact and pressure. If you want durable blades for tough applications, invest in knives made from steel with low Rockwell hardness. You will be required to sharpen them frequently, but they are less likely to break during use.

What is the Best HRC Rating for Kitchen Knives?

The most suitable HRC rating for kitchen knives is anywhere between 55HRC to 60 HRC. Soft and hard steels offer different properties, but this does not make either better than the other. The choice between steel with a high or low HRC rating depends on preference and knife needs. 

Steels with low HRC are more durable, easier to sharpen, and more resistant to pressure and impact but easily become dull. On the other hand, steels with higher HRC offer excellent edge retention, but they are brittle, challenging to sharpen, and should be handled with care and caution.

Therefore, there is no good or bad HRC rating. It all depends on your needs and the budget, Higher HRC knives tend to be more expensive than lower HRC knives like AUS 6 knives.

Can I test Rockwell hardness at home?

Rockwell hardness cannot be tested at home unless you have relevant equipment. It requires an indenter of 150 KGF of force, a piece of steel, special machines, and math calculation skills.

Is the Rockwell testing destructive?

Rockwell hardness testing causes a dent in the steel, but it is not destructive. The dent can also be unnoticeable depending on the tested material’s colour.

Conclusion

The Rockwell Hardness scale helps manufacturers maintain the quality of knives and helps knife users determine the quality of knives. There is no good or bad Rockwell hardness. The choice between low and high Rockwell rating knife steel depends on your preference and knife needs.

If you want a knife with excellent edge retention, go for a high HRC rating of RC60 and above. If you are looking for durable knives that are easy to sharpen and maintain, go for low HRC in the 50s.

If you do not have specific requirements, knives with HRC ratings between 54 and 56 HRC make a good choice because they are not too hard or too soft, and therefore their properties are well balanced.

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