The Knoop hardness test method, also referred to as a microhardness test method, is mostly used for small parts, thin sections, or case depth workIn a Knoop test, a predetermined test force is applied with a pyramid-shaped diamond indenter for a specified dwell time period. The indenter used on a Knoop test is pyramid-shaped but more elongated than the indenter used on a Vickers test. After this dwell period, the force is removed.
Unlike the Vickers test where the indentation length on the vertical and horizontal axes are measured and averaged, the Knoop method only uses the long axis. This measurement is then converted to a Knoop hardness number using a chart.