What Is The Rockwell Hardness Scale

Are you find any number or code like “RC45” or “RC60” on your knife steel or any materials? What is the meaning of this secret code? It is called the Rockwell hardness Scale number of that material.

However, this code is familiar to you, if you are working with steel or cutting materials such as knives, saws, scissors, etc.

History of Rockwell Hardness Scale

Viennese Professor Paul Ludwik was the first person who imagines the depth and hardness of the material in 1908 and includes it in his book Die Kegelprobe. Then a few years later, Hugh M. Rockwell and Stanley P. Rockwell, two brothers invented it and named Rockwell Hardness Scale.

In 1914, the Rockwell brothers worked in a factory as metallurgists. However, at that point, they felt the need to accurately and quickly test the metallurgy for bearing races, and they also needed a clear method for reporting the results.

After that, Stanley P. Rockwell makes a patent of it. In 1919, he improve his method for including it in the Rockwell scale chart.

How Does Rockwell Hardness Scale Work?

The Rockwell Hardness is a scale to measure the hardness of materials. It has no units and is expressed with the symbol HRA, HRB, HRC, HRD, etc. where HR means Rockwell Hardness and the last alphabet means the Rockwell Scale of materials. For example, HRC 45 refers to a Rockwell C whose scale is 45.

Image Source:

Experts are using a process to know the metal hardness accurately which is called Rockwell Hardness testing. This video will give you a good concept for Rockwell Hardness Test.

The knife blade industry follows a predetermined chart of metal hardness ratio, called the Rockwell C scale. The higher number of RC metals is harder than the lower ones. Knife blades mostly use RC45 to RC60 range metal.

We may have wrong thinking that, high range RC means better quality metal. It is totally a misconception about a knife blade. Good or bad relies on the use of the blade. RC45 is more durable than RC60 and has a good withstand impact. On the other hand, RC60 holds its edge for a long time but is brittle.

Is Using Another Knife to Sharpen a Knife Effective According to the Rockwell Hardness Scale?

Sharpening a knife with another can be an effective method, but its viability according to the Rockwell Hardness Scale remains uncertain. The scale primarily measures a knife’s resistance to indentations, rather than its sharpness. While using another knife may temporarily enhance a blade’s sharpness, the scale does not provide direct insight into its long-term effectiveness.


Which is harder Rockwell B or C?

Rockwell scale C is harder than B. Rockwell B always measures the softer metal such as brasses whereas C is for harder metals like steel.

What do Rockwell hardness numbers mean?

It means that a higher number of metals is harder than a lower number. In contrast, the lower number of RC scales is softer than the higher metal.

What is a good Rockwell hardness rating for a knife?

RC 60 or above is a good rating for a kitchen knife. Because they are hard and keep their edge sharpness for a long time, but the dark side is, they are brittle from others.

What is the highest HRC for a knife?

HRC 66 or 67 is the highest for a kitchen knife. But ZDP-189 steel knives can reach HRC 70 if properly heat treated it. On the other hand, TUO brand knives have HRC56±2, which is relatively low.

Final Words

100 year later, Rockwell’s scale is still serving his needs perfectly. This is by far the best method of measuring metal hardness. It is the specific way of reporting the depth of hardness of knife metal, which is used by knife industries.

6 thoughts on “What Is The Rockwell Hardness Scale”

Leave a Comment