How the Rockwell Hardness Scale is Used in Kitchen Cutlery
How do you know if a knife is “tough” or “hard” enough to last? What separates a top-notch cutting tool from a fancy looking blade that will break faster than a fickle teenager’s heart? This is where the Rockwell Hardness Scale comes in – and we’re going to spend some time exploring this topic so the next time you come across a knife brand claiming to have the “sharpest”, “hardest” or even the “toughest” knife, you’ll know the truth.
The Best Rockwell Hardness Rating for Kitchen Knives
In the world of kitchen cutlery, the Rockwell hardness scale is an important tool for measuring the quality of a kitchen knife. With so many different blade options, from carbon steel to several different types of stainless steel – and even, dare we say it, ceramic ? – it can be hard to determine which material is best for the most important tools in your kitchen. Any knife brand can claim to have “the best blade steel”, but you won’t have to take their word for it when you understand the qualities of a knife and how they’re measured.
So, What Makes A Quality Kitchen Knife?
When knife enthusiasts talk about the qualities of blade steel, they’re usually referring to its hardness, toughness, wear resistance, and ability to hold an edge. These terms can be a bit confusing when relying on their basic definitions. While hardness and toughness are synonyms that are often used interchangeably, that’s not the case when it comes to the qualities of blade steel.
Hardness is a measure of resistance to breaks, chips and other deformations when force is applied. This is usually measured by a version of the Rockwell Hardness Scale, which we’ll examine in greater detail in a moment.
Edge Retention refers to how long the blade maintains its sharp edge. Hard materials are known for holding an edge much longer than softer materials, however, they are also prone to chipping and can be more difficult to sharpen.
Durability is a two-in-one when it comes to the qualities of a knife. Both toughness and wear resistance fall under the realm of durability. Not to be confused with hardness, toughness measures how well a knife stands up to heavy use before cracking or chipping, while resistance refers to its ability to withstand adhesion and/or abrasion over time. There are a few different ways to measure toughness, but the general rule is the harder the steel, the less tough it will be.
Corrosion resistance refers to a blade’s ability to resist chemical or elemental breakdown, such as rust. Prolonged exposure to water, salt, acidic foods and abrasive chemicals can all lead to blade corrosion.
The thing to remember is you can’t just max out all of these attributes and have the world’s strongest blade. Remember, you sacrifice hardness for toughness and vice versa. The best blades reach a homeostasis of stats that allow for the best performance in both toughness and hardness, but a knife is like a car – It needs regular maintenance and care.
Now that we’ve covered the qualities of a knife, let’s focus on blade hardness and how it’s measured using the Rockwell Hardness Scale.
What is the Rockwell Hardness Scale?
Invented in the early 1900s by Hugh M. Rockwell and Stanley P. Rockwell, the Rockwell Hardness Scale is a tool designed to provide an equal way to measure the hardness of a variety of materials based on how much pressure it takes to leave an indentation on the surface.
After undergoing several improvements over the years, the scale now offers several different testing scales for different material classes categorized by letters, such as Type A testers for tungsten carbide materials, Type B testers for brass and aluminum, and Type C testers for hard steel materials. When it comes to testing steel used for kitchen knives, the hardness represents the strength of the blade and how well it retains a sharp edge. And the harder the steel, the more wear resistance it has, too.
This is why it’s important to understand the hardness variations in kitchen cutlery when shopping for a new kitchen knife set. Without such a way to gauge strength, you’d be shopping based on descriptions alone (you know – those “best blade steel” claims we mentioned earlier). Instead of just taking their word for it, here’s how the Rockwell scale can help you determine which type of blade steel really is best for your needs.
How to Read the Rockwell Hardness Scale
If you’ve ever looked at the specifications of a knife, you may have noticed a few letters followed by numbers and symbols. The Rockwell Hardness rating is abbreviated to HRC and the numbers determine a material’s ranking on the scale – the higher the number, the harder the material. In other words, the more pressure that is required to indent the surface, the higher the number on the scale will be. Soft materials range up to 52, while anything above that number is ideal for kitchen knives.
As mentioned before, there are several types of Rockwell hardness scales—Type A, B, C, etc. – and each uses different loads and indenters based on the material being tested. Type C is used to measure metal materials for kitchen cutlery, and it’s always denoted as HRC followed by its hardness number.
Other Rockwell hardness types include HRA, HRB, etc. The scale determines the hardness by measuring how much pressure is required to indent the material. It applies a slight pressure followed by a second with an increased amount. The measurement is taken from the light pressure point (marked as the zero position) to the higher number, and the difference becomes the rating.
The test is performed more than once to determine an average rating and confirm accuracy. An HRC rating between 52 and 54 is softer than higher ratings, but it offers less expensive kitchen knives or materials for other applications. An HRC55 or above rating usually represents harder materials and better reliability, strength and longevity.
How is the Rockwell Hardness Scale Used for Kitchen Knives?
As previously mentioned, kitchen knives are measured under the “Type C” category and will have an HRC rating based on the Rockwell Scale. In different terms, the Rockwell hardness scale tests will show you how strong the knife blade is for any particular kitchen knife, and that number is often stamped or printed on the blade or handle.
Typically, the Type C numbers for kitchen knives range between 52 and 60. Therefore, the measurement would be somewhere within HRC52-HRC60, although there is potential for slightly greater variations. Anything below HRC52 would be too soft to be used as a kitchen knife blade.
The number reported for any particular kitchen knife blade represents a value from the scale, rather than a measurement value. The higher the scale number, the higher the strength of the blade. To help understand the numbers better, an axe blade typically falls between HRC45 – HRC55, while kitchen knives usually fall between HRC55 and HRC66. The scale is also very sensitive, which means a single-number difference can actually make all the difference!
So, What is the Best HRC Rating for Kitchen Knives?
When it comes to kitchen knives, the HRC rating really can make or break the quality of a blade. On the lower end of the scale (around 52), you’ll get a very soft blade that may be easy to sharpen, but will have to be sharpened often due to its inability to hold an edge. At the higher end of the scale (anything above HRC62), you’ll get a super hard but very brittle blade that is easily breakable upon impact.
Your best bet for finding quality kitchen knives is to look for an HRC rating around 58 to 60, like F.N. Sharp’s Damascus steel kitchen knives. Coming in at HRC60. F.N. Sharp knives are crafted from premium VG10 Japanese stainless steel to offer extremely durable blades and an exceptionally sharp edge,