Vickers Hardness
Vickers hardness (HV) measures a material's resistance to indentation by pressing a 136° diamond pyramid into the surface under a defined load. The hardness number is calculated from the diagonal length of the square impression using the formula HV = 1.854(F/d²), where a smaller indent indicates higher hardness.
On a CNC shop floor, Vickers hardness testing verifies heat-treatment condition, case depth, and material batch consistency. It is essential for thin, small, or very hard parts where Brinell testing is unsuitable. A lab or quality cell prepares a polished section, applies a known load for a set dwell time, then optically measures the indent diagonals to compute HV. This data guides tool selection—carbide, CBN, or diamond—and alerts to risks of tool wear, edge chipping, burr formation, or dimensional drift from hardness variation. In millwork-adjacent manufacturing, it is used on metal hardware, fixtures, press tooling, bearing surfaces, and fastener components to ensure assembly repeatability and clamp performance.
- Improper surface preparation: A rough, oxidized, or decarburized surface distorts the indent diagonals, yielding falsely low or inconsistent HV readings that do not reflect true bulk hardness.
- Testing too close to an edge or previous indent: Overlapping an edge, weld toe, or prior indent constrains the plastic zone and produces readings that do not represent the material's inherent hardness.
- Wrong load selection for thickness or gradient: A heavy load on a thin case-hardened layer averages through to the softer core, while a light load on coarse-grained material gives noisy, unrepeatable results.
Why use Vickers instead of Rockwell on a CNC-controlled production part?
Vickers is preferred for micro-scale resolution, thin sections, case depth profiling, or hardness mapping across welds and coatings because it measures the indent optically rather than relying on depth alone.
What does an HV designation like HV10 mean?
The number following HV indicates the applied load in kilograms-force. For example, HV10 means the Vickers test was performed with a 10 kgf load.
Why is the indenter angle 136°?
The 136° diamond pyramid geometry creates a standardized square impression that works across a broad range of materials and hardness levels, making the test widely applicable for metals.