If you’ve ever looked on the packaging of your knife you may have found a small section with the letters HRC and a number beside it. This is a way that the manufacturer is trying to speak to you on how to best use the knife and what it’s rated for! HRC is the Rockwell Hardness Score and we’re breaking it down for you!
This handy little number can be incredibly important to understand if you want to keep your knives and tools in top condition!
It’s important to note here that there are several different kinds of scales and factors that go into each Rockwell Hardness scale and Rockwell Hardness test. For the purposes of this discussion we’re going to speak more superficial rockwell scales generally so that you have a working base knowledge applicable to most people.
The Too Long, Didn’t Read Version: the Under 58 Second Brief!
Rockwell Hardness and your knives.
When it comes to knives, and knife making there are several different factors that a blacksmith might contemplate when planning their edges. One of the larger considerations is how hard the metal might need to be in order to perform the work it’s designed for.
Given that there are so many different kinds of metals out there it became difficult to convey a subjective measurement of “hard metal” between different brands. Think of it this way, one person lifting a 45 lb kettlebell might be heavy, and to a body builder it might feel light. Over time a need for a scale and test of superficial hardness of metallic part was needed to make sure that there was a standard form of reporting was available.
It is now common practice for a Rockwell hardness number be printed on packaging or used in reporting specifications using the marker HRC, and the scale runs from 1 to 100.
Note: Thin Steel and soft or thin materials.
Rockwell hardness scale is not a measurement of how thin steel a given edge is, but how hard the metal is.
The Rockwell Hardness scale
In the case of the Rockwell Scale, getting a 100 in hardness testing isn’t always better. For most applications, the majority of people are best served with something in the 50-70 range regular rockwell scales. General consensus is that a knife that tests below a 50 might be too soft of material to hold an edge long term and require more sharpening (That said, if you do have one that needs more care, we’d love to help you sharpen it.) On the other hand knives and edges that rate above a 70-75 will start to get brittle.
How we use the Rockwell hardness scale.
In order to put the Rockwell hardness testing to work for you it’s helpful to think of it like a sliding scale depending on a few factors. Our general rule for it is that the harder the edge metal is the thinner it can be and still hold the sharpness. However the other main factor is the brittleness. If it is a knife you’ll use for survival situations you want a much less brittle edge that will be thicker.
If you’re in the wilderness then you’re likely going to be cutting through tree limbs and making kindling as an example we can use. For these purposes we would suggest looking for a larger knife that can stand up to being beaten on, this knife might have a lower hardness value however it will actually perform much better. Overall this might be around a 50-55 HRC value and it may be made of an alloy of different metals. You can grab a FREE list of our favorite field knives here!
Most chefs tend to like thinner and harder metals for their chefs knives. It allows them to work longer and still be able to hold an edge sharp. So in this case the hardness test would come back with a Rockwell hardness of 65+ and it would be very important not to drop them due to the increased brittleness of the metal. We talk about some of the best chef’s knives here!
The Rockwell hardness testing method?
The answer to this question largely depends on what Rockwell Hardness Scale you’re using and for what purpose. That said, most Rockwell hardness scales follow the same basic principles or indentation hardness.
The metal is placed onto a surface and a point of the hardness tester is placed on the face. From there increasing forces are applied to the point from minor load to major load until an indentation is able to be measured.
What about medium case hardened steel?
So an edge made from softer steels would indent faster than a hardened steel would regardless of how thin steel it is made of. More than that the Rockwell hardness score can be used if the metal has had shallow or deep case hardening used to help fortify the metal.
Also the indentation process has the potential to be effective for the total make up of the metal surface which could be effected by shallow case hardened steel or deep case hardened steel (but that’s another article!)
Also of note there is a few superficial Rockwell hardness scales that are more specific and ranks each by shallow case hardened steel, medium case hardened steel, and deep case hardness and rockwell superficial and hardened steel.
Key Takeaways For The Rockwell Scale And The Rockwell Hardness scale
When looking for your next knife or if you’re just looking to get to know it better then knowing it’s up to the task is a great place to start. Now you know if it’s made of soft or thin materials then it has better uses for other tasks then helping you baton down a branch into firewood.
Remember that HRC is your Rockwell hardness number and knowing what it is, you can help take better care of your tools by knowing how often and to what degree sharpening and honing is going to be needed.
Finally, for most people you don’t need to know the difference between Rockwell c scale, Rockwell b scale, and other Rockwell hardness tests. You simply just need to know how to understand what it’s telling you to help it work at its best for you!
Frequently Asked Questions
What is a Rockwell hardness test?
The Rockwell hardness test is a method of determining how hard, soft or potentially brittle a given metal is based on various loads applied to hardness testers. Soft steels will have a lower number and harder steels will have a higher number. However at a certain point the metal can get too hard and become brittle under certain conditions.
How do I read Hardness values?
The hardness value will typically be stamped or marked by HRC followed by its score. That score is based on a 1-100 scale and are based on its test method under minor and major loads.
When would Rockwell hardness and the Rockwell test be beneficial?
Typically the Rockwell hardness score and scale is beneficial when looking at what your edge can perform reasonably, repeatably, and without requiring a lot of upkeep to do so. The answer to this question is similar to the question of “how often should I sharpen my knife?” which our response is as often as needed to do the job you require of it.
Is softer steel bad in knives?
Soft steel isn’t always a bad thing, but to keep its edge it will usually need more maintenance than a harder edge. You can find a plethora of soft steels on the market, and they are usually at a cheaper price.
A great example is beginner chefs knives are usually a softer steel than a professionals. That doesn’t make them bad if you’re just starting and accept the need to sharpen more often.
That said, if it’s a field knife a soft steel could make things more difficult. Aim for a thicker metal and a score in the 50’s to be able to stand up to the work. Extremely hard steel might also not be beneficial to you in the field as it could be too brittle for use under those conditions.
Can I Perform My Own Hardness Test?
We DO NOT recommend trying this yourself. Indentation hardness is something that requires special equipment that can handle various minor load forces and major load pressures. The Rockwell test can be dangerous to perform without proper training and equipment and should not be performed by anyone other than certified personnel.
Looking for a more in depth read on Rockwell Hardness? We recommend this article! https://www.mee-inc.com/hamm/rockwell-hardness-testing/