Because of it’s somewhat complicated nature, hardness is a variable that a lot of new knife collectors often overlook when considering or even comparing knives. This lesser talked about characteristic can be make or break a blade however, and should always be one of the main factors you look at during the knife buying process. In this article we will explain the standard system that is used to measure hardness as well as the implications that hardness has on a knifes performance and lifespan.

The Rockwell Hardness Scale

Invented by Hugh M. Rockwell and Stanley P. Rockwell, in the early 1900s, this method of measurement uses a weight baring impactor to determine the hardness of any material. 

More specifically, a pointed “impactor” is pressed into the surface of the material being measured until it indents. This point of indentation is used in combination with the weight of the impactor to calculate the RH rating. The type of material being measured determines not only the weight/force used in the process but also the material of the impactor itself. Softer materials like copper or zinc will be impacted with a hard metal sphere whereas harder materials like iron or steel will be impacted with a diamond sphere. Because knives are generally constructed from harder metals like steel, they are usually tested with a diamond sphere impactor and are categorised as an HRC type on the Rockwell Hardness scale.

How hard should a knife be?

This highly depends on what you want out of the knife. Harder knives will hold an edge for much longer but are slightly more difficult to sharpen and also do not offer much flex. Softer knives on the other hand won’t hold an edge for very long but will offer some flex. Generally a chef’s knife should be as hard as possible whereas something like a boning knife, which might benefit from some flex, can be made from a softer metal. More often than not however, a harder knife is better.

A good knife should sit anywhere in 53 - 57 HRC range, and a really strong knife will sit anywhere above that. Steels like Damascus are carbon steel are generally very hard and will sit around the 60 HRC mark. This is thanks to the repetitive layering process used during their constructions.

Hardness is not the be all and end all though. Another common mistake that beginners make is getting a very hard knife and then not bothering to maintain it at all. A soft knife that is stored properly, used appropriately and sharpened frequently will out perform (and out last) even the hardest knife that is not cared for correctly. If you don’t know much about sharpening and are wanting to learn more, we recommend you check out our previous article about whetstones. 

A whetstone is traditional sharpening tool that is arguably the best way to keep your knives sharp and preserve their edges for long into the future. In terms of storage, storing your knives in a material knife roll or on a magnetic wall hang are both great non-damaging methods that we recommend.

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