The tool generally uses the Rockwell Hardness HRC system, which is used to measure the heat-treated metal tool.
The hardness of commonly used tools is generally around 50. The improvement of hardness requires high-quality raw materials and the technical level of heat treatment. No matter how the rotten material is treated, it will not show good hardness. Failure of heat treatment will turn good materials into garbage. General household kitchen knives are in the range of 50-55, which is easy to manufacture and polish. The hardness of high-quality folding knife is above 55 and below 60, which can keep sharp and tough for a long time. However, extreme hardness and toughness are closely related to materials and heat treatment. Ordinary spring steel can have very high hardness if it is subjected to extreme heat treatment, but it has almost no toughness, and it may break directly when quenched.
The hardness of high-quality military tools ranges from 55 to 65, depending on the tool classification. The main battle knives are generally in the range of 58-60, while some luxurious hand knives and high-quality sabers are about 60-65 in hardness, which are generally more expensive. Due to the use of higher grade steel and stricter heat treatment, these high hardness tools still maintain good toughness. However, there are also some records of expensive tools breaking due to insufficient toughness. It is generally understood that heat treatment is not enough.
There are also knives with ceramic blades now. The hardness of ceramics can not be measured by HRC system, and the hardness range of materials is close to that of glass, which belongs to ultra-high hardness. However, after practice, its elasticity is very poor, so apart from kitchen knives, which can only do light work, heavy knives such as military knives or camping knives rarely use ceramics for people.