If anyone asks you what is Rockwell hardness for knives, the simple answer is – HRC is the unit of measure for blade hardness.
Just as the degree Celsius measures the temperature (currently I am writing at 15°C) or as the meter defines the distance from one place to another (my office is 800m away from home), the HRC indicates the hardness of the knife blade.
HRC stands for:
- H ardness value of the blade = How hard is the blade steel?
- R ockwell = The measuring method named after the inventor Stanley Rockwell (more on that later)
- C one = The scale on which the value moves (Cone stands for diamond cone, with which the measuring procedure is carried out)
This is how you say it:
The chef’s knife from kitchen sharp has a hardness of 57 Rockwell (57 HRC).
Nesmuk knives, on the other hand, have a Rockwell degree of 60 HRC.
The inferior knife steel is comparatively very soft and only has around 50-52 Rockwell.
But what does the hardness of a blade say about the knife?
Do high-quality kitchen knives have to have a high Rockwell grade?
No, it’s not that simple.
The blade hardness does not tell you whether your knife is of high quality, but for what purpose you can best use it.
A cleaver has a broad blade and soft steel so that the knife edge does not break immediately when it hits bone or frozen food, but remains “elastic”.
However, a high-quality chef’s knife usually has a higher blade hardness, which means that there is less wear when cutting. This keeps the knife edge sharp for longer.
But before I tell you what the degree of hardness according to Rockwell tells you about your knife, the two of us will take a short, crisp trip to the workshop and take a close look at the Rockwell knife process.
How does the Rockwell hardness test work? Simple Explanation!
How to do it:
A rounded diamond cone with a 120° angle is pressed twice into the knife steel.
First, the cone enters with a force of 98.07 Newtons – this is the pre-force.
After that, the force is increased to 1372.93 Newtons and the cone continues to penetrate – this is the main force.
This pressure is held for a few seconds, after which the main force is removed.
What remains is the initial force of 98 Newtons and the remaining penetration depth (e).
Finally, the degree of hardness is determined using the following formula:
HRC = (0.2 – e)500
i.e. [(0.2 minus permanent penetration depth)*times 500]
By the way…
Only steel can be checked this way – no ceramic blades.
Nevertheless, you sometimes see that the hardness of a ceramic knife is indicated by an HRC value.
That’s not entirely true, but it’s justifiable.
The Kyocera Kizuna is a ceramic knife and is much harder than Damascus steel. In order to have an approximate comparison, an estimated HRC value is usually given – in this case ±80 HRC for the Kyocera Kizuna chef’s knife.
Let us discuss about your knife.
Let’s move on and examine the most important question:
What does the degree of hardness tell you about your knife?
How do you recognize a good, high-quality piece of furniture for your home?
Mostly, the material, right?
Here’s an example:
A chest of drawers in the bedroom is robust, stable and of high quality if it is made of real wood – for example, German oak.
A cheap sideboard in the student apartment, on the other hand, is soft and “brittle” if it is glued together from pressed chipboard.
Real wood does not always have to be hard.
A cot can be high-quality and robust – but it can also be soft, for example, if it is made of soft cherry wood, it does not hurt the children if they bump their heads against it.
It’s the same with knives…
The degree of hardness only gives you limited information about the quality of your knives.
However, you can use the following degree of hardness as a guide:
High-quality kitchen knives usually have a blade hardness of at least ±54 HRC.
For all other knives that are in the lower degree of hardness, you should find out exactly what steel it is, how the knife was processed, etc.
But there are also 3 important pieces of information that the degree of hardness according to Rockwell reveals about your knives:
- Whether your knife has hard or soft steel.
- How high is the edge retention – how long does the knife stay sharp?
- How well can you resharpen it when the blade has become dull?
Let’s take a closer look:
1) Hard Steel and Soft Steel – Differences?
That’s about the range on the Rockwell scale.
The lowest value is about 52 (with really rancid steel even 50 HRC – but that is rather rare).
The highest value is 67 HRC – depending on the type of cut and different hardening processes, it can even rise to 71 HRC in individual cases.
Here is an overview of the degrees of hardness according to Rockwell:
50 – 52 HRC = usually “cheap knife” for 5-10 $ in the supermarket
You should stay away from such knives.
They are mostly mass-produced from cheap steel, rust more easily and are poorly finished.
But the biggest disadvantage is:
The steel is so soft that you will notice how quickly the cutting edge wears down over the course of the day.
If you cut a tomato for breakfast in the morning and cut a tomato for a salad in the evening, you will find that your knife doesn’t slide through the tomato so smoothly anymore.
53 – 54 HRC = soft steel, flexible blades
- Especially common in outdoor knives, bushcraft knives and solid “entry-level” kitchen knives (e.g. Zyliss, Jamie Oliver)
From 53 Rockwell the better knife steel begins.
Kitchen knives in the low price segment ($30 – $40) often have around 53 – 54 Rockwell and are more suitable for entry into the world of blades.
Because the knives are flexible and forgive a lot of mistakes when cutting, since the cutting edge is usually sharpened at a wide angle and does not break if you handle it clumsily.
In addition, many axes and outdoor knives commute in this area of the scale and sometimes cost over $200.
The degree of hardness of the blade steel says more about the purpose than about the quality of a knife.
55 – 56 HRC = typical blade hardness of European kitchen knives
- High-quality blade steel (X50CrMoV15) for German knives from Solingen (e.g. Zwilling, Felix, WMF)
The highest quality kitchen knives in the world are forged in Solingen and usually have a blade hardness of 55-56 HRC.
The “Solingen blade steel” X50CrMoV15 is used as the basis and some manufacturers harden the knives through additional hardening processes (see below).
The knives are still flexible and because the steel is soft, you can sharpen the knives particularly easily and quickly – even as a beginner.
57 – 59 HRC = high quality knife steel
- The steel is hardened using special hardening processes and grinding techniques (e.g. Güde, Küchenspitz, Wüsthof )
The upper knife class (70 – 150$) settles with a blade hardness of 57-59 Rockwell.
Here, too, the knives are forged in one piece from the X50CrMoV15 and are additionally hardened and made more resistant to acids using various techniques, for example, blue-glazing, ice-hardening or the Solingen thin grinding.
Such kitchen knives are particularly interesting for amateur cooks, as they remain sharp for a long time – but can also be easily resharpened.
60 – 64 HRC = hard premium steel
- As a rule, Japanese knives are forged in this Rockwell area, but also Damascus knives or special alloys (e.g. Nesmuk knives)
These knives are ground particularly thin, which is why they are extremely sharp.
Such knives are only suitable for the professional chef, since the blatant sharpness of the blade is more of a disadvantage in the hands of a layman.
Because knives of such sharpness and hardness don’t tolerate mistakes and the blade will break off at the slightest clumsy movement – or you’ll just hurt yourself.
64 – 70 HRC = Japanese premium steel
- Very few masters in Japan forge such blades.
The hardest blade steel in the world (ZDP-189 ) consists of 20% chrome and has a carbon content of 3%.
Well-known manufacturers are, for example, Spyderco, Al Mar Knives, Kiku Knives or Rockstead.
Now you know when a knife is made of hard steel and when it is made of soft steel.
But what does the hardness of the blade say about the edge retention of the individual knives?
How long does a knife stay sharp?
You can see that here:
2) Edge retention of the kitchen knife
The fact is:
The harder the knife steel, the longer the blade stays sharp, right?
In practice, however, it depends on you.
With a hard blade, there is less wear and the cutting edge wears down more slowly – you already know that.
But if you handle the knife wrongly, say:
- Improper cutting technique
- Much too hard cutting mat
- Wrong clippings
Then your knife will dull even faster than a blade made of softer steel. How come? Because hard knife steel does not forgive mistakes.
In other words:
- If you cut frozen food with a 60 HRC chef’s knife, the knife edge can break off quickly.
- If you use a glass, ceramic or granite cutting board and cut too harshly, the blade can collide with the harder cutting surface and break off as well.
- If you cut sloppily or use the wrong cutting technique, you can both hurt yourself and break your knife.
By the way, I’m going to show you 21 cutting techniques here that you can use to cut like a pro and are guaranteed to never cut your fingers again.
But let’s stay on topic:
Soft knife steel, on the other hand, is flexible and the cutting edge is not as unforgiving as a pubescent teenager – but quickly forgives mistakes because the cutting edge is not “at risk of breaking”.
Soft steel wears more wear and a sharp blade doesn’t stay sharp as long – so you’ll need to regularly sharpen the knife to keep it sharp.
But how well can the different degrees of hardness be sharpened?
Let’s look at this now:
3) How well can a knife be resharpened?
Soft steel is pliable, making it easier to sharpen back into shape or sharpen to the right angle.
Hard steel is stubborn and can only be sharpened again with special knife sharpeners.
And when a knife has become dull, 2 things happen.
Let’s take a look at what these are:
3.1 First, the knife becomes dull.
Before the knife is dull and no longer cuts at all, it is rather dull and can just about cut one or the other tomato.
In this case, the cutting edge has a fine, barely visible curve and is no longer pointed like a V – but more like a y (this curve is called a ridge).
You can quickly get that back into shape and sharpen your knife with a sharpening rod.
“Bend” the blade back into the pointed V-shape.
With a blade hardness of up to 56/57 HRC, this is easy and even a beginner can do it with a simple sharpening steel.
I’ll show you in a moment what it looks like with hard steel from 58/59 – so stay tuned.
By the way, here you can see which knife sharpeners are available and what you can use them for.
But what happens if you don’t sharpen your knife in time?
3.2 Then the knife becomes really blunt.
The cutting-edge rounds and the V-shape wear down to a U-shape.
Then only one thing helps:
Grinding – i.e. removing material.
With soft steel up to 57/58 HRC, this is still easy and you can do it yourself as a beginner.
A simple sharpening stone is sufficient for this.
In this simple crash course, I’ll show you how to sharpen a dull knife extremely sharp.
But all this becomes problematic from a Rockwell hardness of 59/60 HRC.
On the one hand, the blade steel is very hard – but also very sensitive.
You not only need special tools such as a squeegee, ceramic stick or diamond-grit sharpening tool, you also need the right technique.
On the other hand, you cannot sharpen hard knife steel (from 59/60 HRC), you can only grind it – at the right angle with the right water stone.
As a beginner, it’s best to go to a professional sharpening service.
Advantages and disadvantages of different HRC values
That was a lot of stuff.
So that your head does not burst, I have made an overview for you.
Here are the pros and cons of soft and hard steel:
|Soft steel 54 HRC – 57 HRC|
|Shatterproof, resistant to impacts||Beginner-friendly, ideal hardness for beginners. Does not break with the wrong cutting technique|
|Versatile for cutting both soft and hard materials||Limited grinding for a fine edge. “Maximum” angle of ± 20° (the more acute the angle, the sharper the blade)|
|Beginner-friendly, ideal hardness for beginners. Does not break with wrong cutting technique||Blade wear and reduced long-term sharpness|
|Easy to sharpen using a sharpening steel or whetstone||Greater wear due to universal cutting usage|
|Flexible, suitable for various cutting techniques|
|Can be used for chopping, filleting, and most of the cutting techniques||Regular sharpening is required to maintain sharpness|
Here are the advantages and disadvantages of HRC 59 – 67 steel blades:
|Hard steel 59 HRC – 67 HRC|
|Ideal for precise and filigree cuts||Prone to breakage if used incorrectly|
|Cutting edge has an acute angle (approx. 15°) which is extremely sharp||Limited to precise and clean cuts only (Chopping not possible)|
|Lighter weight than soft steel due to a narrower blade||Requires special knife sharpeners for sharpening (water stones, slip leather, ceramic rods)|
|Sharpening required after a longer period||Unsuitable for cutting frozen or hard foods|
|Hard Japanese steel (65+ HRC) can be ground extremely fine and sharp||Rigid and inflexible blade, susceptible to breaking on impact|
|Sharpening required after longer period|
|Meets professional chef’s sharpness requirements|
What did you notice?
There are enough pros and cons with soft steel – and enough with hard steel.
That’s why there is no “best” knife steel.
The question is much more about which knife suits you best.
And you can derive that very well from the degree of hardness for you.
So we ask ourselves the final question:
What Rockwell hardness should your chef’s knife have?
Let’s get to the point:
Can you handle a knife or not?
If you didn’t immediately answer the question with a YES, then professional knives with 59+ HRC are not for you.
You need something to get you started.
A good balance between hard and soft.
A universal knife with 56 – 57 HRC.
I recommend you my favorite knife.
Thanks to a special ice-hardening process and a traditional Solingen grinding technique, the blade is sharp – and stays that way for a long time.
Alternatively, you can also get a Güde knife.
As a rule, the chef’s knives also have 57 HRC and go through similar hardening processes and grinding techniques as our kitchen sharp selection.
You’d just have to dig a little deeper into your pocket.
Because you’re also paying for the name.