A knife is a common household tool with various uses but mainly for cutting different things ranging from vegetables that are very soft to the wood of the hardest kinds. Therefore, the hardness of the knife is very important first to assure that it can cut what it is intended for, and secondly for its durability. However, the hardness of a knife could indicate the level of brittleness and durability when used. For example, harder knives with high hardness values are not easily deformed at the edge like their softer counterparts.
Nonetheless, softer knives are more durable and are not susceptible to chippings or breakage like the harder knives. Hence, the need to be careful with harder knives so that it does not chip off at the thin edge.
Therefore, producers can determine a suitable hardness when producing blades and knives. For high impact blades like chisels and axes, softer blades are required, while hunting knives often use harder steel to maintain a sharp edge.
A high hardness value is most important for knives used for tough and extreme cutting, and durability will be an essential consideration for knives to be used for chopping.
How to test hardness in knife making
The need to test cutting tools for hardness is essential to ascertain their durability and cutting ability. There are different means of testing the hardness of knives, but the most popular in the knife making industry is the Rockwell hardness test.
Most knives have a Rockwell hardness number attached to them that you will see when purchasing them. For example, RC60 means the knife has a Rockwell hardness number on the C scale.
But how does the Rockwell hardness test work?
Rockwell tester uses an indenter that has a conical or ball-shaped head as a static load. The load is applied to the knife for a specified time to cause an indentation. This depression is measured and compared to the Rockwell C scale to arrive at the knife’s hardness.
This process is always in two phases.
The first phase uses the conical-shaped device as a slightly lower load of 10kg to cause an indentation. The indentation depth is measured and recorded.
The second phase uses the ball-shaped device as a heavier load of between 60kg to 150kg on the first indention spot. A new indentation caused by the second load is measured and recorded. The difference in the first and second indentation reading is calculated and compared against the standard Rockwell C scale to determine the knife’s hardness.
The range for hard knives often falls between the RC50 and RC60, while that of soft knives are generally RC40 values on the Rockwell hardness chart.[adsense]
However, since the indentation measured on softer metals are higher than that of harder metals, it implies that the Rockwell hardness number is inverse to the indentation measured. The Rockwell hardness number is standard in the knife-making industry as it helps manufacturers quickly assess a knife’s hardness on sight.
Where to buy the hardness tester?
If assessing the hardness of your knives is important to you, then getting a hardness tester might be an option for you.
However, where you get your hardness tester is equally as important as the need to get a tester. You might also want to consider some criteria like the level of tester accuracy, the range of hardness you are looking at, and how flexible the tester is before purchasing it.
Hardness manufacturers vary in their expertise and the accuracy of their testers. You should consider a company with a wealth of experience in the hardness tester industry and is involved in research for improved solutions for hardness testers.
AOLI Shenzhen Technology Co. Ltd.
This is a company that specialized in the research, development, and production of metal and non-metal material hardness testers. They are one of China’s early site R&D and manufacturing reliable bases for hardness testers.
AOLI Shenzhen Technology Co., Ltd also works with clients to provide solutions tailored to individual testing needs with high precision hardness testing machines.