In Gage Threadcheck's Official Blog

Knoop Hardness Testing

In the Knoop hardness test, a diamond pyramid indenter, which has a rhombic base with included angles of 172°30' and 130°, is pressed onto the specimen under a test force F (kgf). The hardness number (HK) is obtained by dividing the test force F by the projected area, A (mm2), of the identation. The area is calculated from the longer diagonal length, d (mm), of the indentation when the indenter is removed.

The Knoop hardness scale is generally used when shallower depth indentions are required. Knoop hardness can be measured by installing a Knoop indenter on the Macro-Vickers hard- ness testing machine.

 http://www.threadcheck.com/hardness-testing/

Vickers Hardness Testing

In the Vickers hardness test, a diamond pyramid indenter with a 136° angle between oppo- site faces is pressed into the specimen under a test force F (kgf). The hardness number (HV) is obtained by dividing F by the area, A (mm2), of contact between the indenter and specimen. This area is calculated from the diagnonal length, d (mm), of the indention when the indenter is removed.

The Vickers hardness test is the most versatile hardness testing method of those that use different load settings. The Micro-Vickers hardness test, which accepts load settings of 1 kgf (9.807N) or less, is especially well suited for industrial production today, where accuracy requirements are increasing due to technology improvements. Vickers hardness testing at loads 1 Kilogram and up is also known as heavy loead Vickers or Macro Vickers. The other testing parameters are similar to lighter load vickers testing. This type of testing may be used to meet the requirements of international specifications or to replace Rockwell testing.