Metallurgical · hardness

Hardness tester calibration (Brinell, Rockwell, Vickers)

Foundry and metallurgical labs live and die by hardness numbers. Keeping a hardness tester honest means direct verification of what it applies and indirect verification of what it reads.

By Versatile · equipment manufacturer & calibration provider · updated 2026-07-15

The governing standards

Each standard has multiple parts - the machine, the test blocks and the indenters are covered separately. Calibration and verification follow those parts.

Direct verification

Direct verification checks the machine's own elements against traceable references: the test force at each level, the indenter geometry, and the measuring system (depth for Rockwell, optical for Brinell/Vickers). It is typically done at installation, after a move or repair, and periodically.

Indirect verification with test blocks

For a tester in daily use, indirect verification with certified reference test blocks is the everyday control. A common procedure (per ISO 6508-2 / ASTM E18) is:

• Use NIST-traceable test blocks covering low, mid and high hardness for each scale in use.
• Take five readings on three blocks per scale (low / mid / high).
• Compare the mean and spread against the block's certified value and the standard's tolerance.
• A good service also inspects and cleans the tester, reviews the daily-check log and confirms the correct loads and indenters are fitted.

How often

A daily indirect check on one block per scale in use is good practice regardless of the formal interval.

Common problems

• Worn or chipped indenter - especially the diamond on Vickers/Rockwell C.
• Dirty or damaged test block face.
• Poor specimen support - a rocking part reads soft.
• Wrong dwell time or load for the scale.
• No traceability on the blocks - the certificate must state standard, method, results and uncertainty.

Frequently asked questions