You may have heard of Knoop and Rockwell hardness measurements. But what is their relationship? Do they all mean the same thing? If you’re planning to purchase a hardness diamond indentor, you’ll need to know what each one means. Read on to learn more about this important test. This article will help you determine the right one for your project. This article also covers some of the lesser known Shore scleroscope and the Vickers hardness method.
Rockwell Hardness
A variety of hardness tests are used to measure the strength of materials. Indenters have different hardness ratings, which are commonly referred to as Rockwell hardness. The hardest materials are usually tested with a diamond cone. Hardness numbers are obtained by applying loads and measuring the depth of an indentation. Softer materials, such as steel, are tested with a steel ball. Hardness values are correlated with the materials’ elastic properties.
Diamond indenters can be used to measure Rockwell hardness. Diamonds have a hardness of 60. Abrasive materials, such as glass and plastic, are hardest. The Rockwell hardness of steels is the number that describes how easily a stone or metal can be cracked. Diamond indenters have the highest Rockwell hardness rating, while abrasive materials are softer.
Vickers Hardness
A Vickers hardness tester is a diamond tool that makes an indentation on a surface by using a high-pressure. The resulting indentation is the Vickers hardness number. This number is the same for every diamond, but it’s much more accurate for synthetic diamond. The Vickers hardness number is measured from an average of three readings.
It’s important to note that a Vickers hardness number is expressed in kilograms-force per square millimeter, not in kilograms-force-per-square-meter. Hardness units are often reported in newtons, which is meaningless for most engineers and technicians, but still an important consideration. That being said, Vickers hardness measurements are the most common. And they’re worth every penny.
A Few Other Types of Hardness Indenters
There are other two types of diamond indenters used in hardness testing: Vickers and Knoop. Both types can produce the same results, although a Knoop hardness indenter penetrates the specimen about half as deep as a Vickers indenter. Neither method has a special advantage over the other, but both methods are suitable for hard materials and thin layers. The Knoop method uses a diamond pyramid indenter, which is longer and wider than the Vickers indenter. The indentation length is measured on the long axis of the test, and the resulting number is translated into a Knoop hardness rating.
The results of a Knoop indenter are numerical, and repeatability is usually within two to five percent of the initial value. Some crystals exhibit large variation in hardness, which may be caused by a number of factors, including the orientation of the test surface.
A Shore scleroscope measures the hardness of various materials by measuring the rebound hardness. The instrument consists of a graduated glass tube that has a diamond-tipped hammer that is dropped into the material under test. The height at which the hammer bounces back increases with the harder the material is. The higher the rebound height, the higher the hardness value.
In Conclusion
The hardness of a material is determined using its elasticity, not its density. In the case of steel, for example, the height of the first rebound is the index of hardness. The hammer that makes the impact can also measure the material’s elasticity.
Kutwel Diatools manufactures certified hardness diamond indenters and assigns certificates of compliance to each one. Hardness diamond indenters are available for most Hardness Testers. A hardness diamond indenter works by pressing a sphere or a diamond cone into an inelastic material. The load is measured in kilograms and units. The impression should be one tenth of the material’s thickness. The test can measure the hardness of metals, ceramics, or other materials with a variety of hardness levels. Typically, diamond indenters are used for materials whose hardness is above 300 HB/30.
