Overview
EN ISO 4545-2:2018 (identical to ISO 4545-2:2017) specifies methods for the verification and calibration of Knoop hardness testing machines used on metallic materials in accordance with ISO 4545‑1. The document defines both a direct verification/calibration route (for test force, indenter and diagonal measuring system, and testing cycle) and an indirect route using calibrated reference blocks for overall machine checks. It is intended to ensure traceable, repeatable Knoop hardness measurements across laboratories and production facilities.
Key topics and technical requirements
- Direct verification elements
- Calibration of test force: each force used shall be measured (at multiple plunger positions if force varies with position). Calibration may use an elastic proving device per ISO 376:2011 (class 1 or better) or by balancing with calibrated masses (accuracy ±0.2%).
- Verification of the indenter: checks to confirm indenter geometry and mounting are correct (see ISO 4545 series for indenter specifics).
- Calibration/verification of diagonal measuring system: requirements for accuracy of the optical/measuring microscope used to measure Knoop indentation diagonals.
- Verification of the testing cycle: ensures load application/removal and timing do not introduce errors.
- Indirect verification
- Uses reference blocks (calibrated per ISO 4545-3) to check the overall system performance and comparability of hardness levels.
- Measurement conditions & traceability
- Direct verification recommended at (23 ± 5) °C.
- Instruments used must be traceable to national standards.
- Procedures address uncertainty of calibration/verification, repeatability and bias assessment.
- Operational rules
- If a machine is used for multiple hardness methods, it must be verified independently for each method.
- Verification schedules and reporting requirements are defined, including content of calibration certificates.
Applications and users
- Quality control and metrology laboratories performing Knoop hardness testing on metals.
- Manufacturers of hardness testing machines and calibration houses that provide verification services.
- Metallurgists, materials engineers, and R&D labs needing reliable, traceable hardness data for:
- production QC and incoming inspection
- material certification and acceptance testing
- failure analysis and research where precise microhardness is required
Related standards
EN ISO 4545-2:2018 provides the procedural and metrological framework to achieve consistent, traceable Knoop hardness results - a cornerstone for accurate microhardness testing in industry and laboratories.
