EN ISO 4545-3:2018

• Abstract:

  ISO 4545-3:2017 specifies the method for the calibration of reference blocks to be used for the indirect verification of Knoop hardness testing machines as specified in ISO 4545‑2.; The method is applicable only for indentations with long diagonals ≥0,020 mm.

• Status: Published
• Publication Date: 06-Mar-2018
• Withdrawal Date: 29-Sep-2018
• ICS: 19.060 - Mechanical testing
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Drafting Committee: ECISS/TC 101 - Test methods for steel (other than chemical analysis)
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 07-Mar-2018
• Completion Date: 07-Mar-2018
• Ref Project: SIST EN ISO 4545-3:2018 - Metallic materials - Knoop hardness test - Part 3: Calibration of reference blocks (ISO 4545-3:2017)

• Replaces: EN ISO 4545-3:2005 - Metallic materials - Knoop hardness test - Part 3: Calibration of reference blocks (ISO 4545-3:2005)
• Effective Date: 14-Mar-2018
• Refers: ISO 376:2011 - Metallic materials — Calibration of force-proving instruments used for the verification of uniaxial testing machines
• Effective Date: 09-Feb-2026
• Refers: ISO 4545-2:2017 - Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing machines
• Effective Date: 09-Feb-2026
• Refers: ISO 4545-1:2017 - Metallic materials — Knoop hardness test — Part 1: Test method
• Effective Date: 09-Feb-2026
• Referred By: EN 60950-22:2017 - Information technology equipment - Safety - Part 22: Equipment to be installed outdoors
• Effective Date: 09-Feb-2026
• Referred By: EN ISO 3452-5:2008 - Non-destructive testing - Penetrant testing - Part 5: Penetrant testing at temperatures higher than 50 degrees C (ISO 3452-5:2008)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 23278:2015 - Non-destructive testing of welds - Magnetic particle testing - Acceptance levels (ISO 23278:2015)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 23277:2015 - Non-destructive testing of welds - Penetrant testing - Acceptance levels (ISO 23277:2015)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 23278:2009 - Non-destructive testing of welds - Magnetic particle testing of welds - Acceptance levels (ISO 23278:2006)
• Effective Date: 28-Jan-2026
• Referred By: CEN ISO/TS 25108:2018 - Non-destructive testing - NDT personnel training organizations (ISO/TS 25108:2018)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 18081:2024 - Non-destructive testing - Acoustic emission testing (AT) - Leak detection by means of acoustic emission (ISO 18081:2024)
• Effective Date: 28-Jan-2026
• Referred By: EN ISO 23277:2009 - Non-destructive testing of welds - Penetrant testing of welds - Acceptance levels (ISO 23277:2006)
• Effective Date: 28-Jan-2026
• Consolidated By: ISO 4545-3:2017 - Metallic materials — Knoop hardness test — Part 3: Calibration of reference blocks
• Effective Date: 12-Feb-2026

Overview

EN ISO 4545-3:2018 (ISO 4545-3:2017) specifies the method for the calibration of hardness reference blocks used for the indirect verification of Knoop hardness testing machines (see ISO 4545‑2). The procedure is intended for indentations with long diagonals ≥ 0.020 mm and defines manufacturing, dimensional, surface and calibration-machine requirements to ensure traceable, repeatable Knoop hardness measurements.

Key topics and requirements

• Scope and applicability
  • Calibration method for reference blocks used in indirect verification of Knoop hardness testers.
  • Applicable only for Knoop indentations with long diagonals ≥ 0.020 mm.
• Reference block manufacture
  • Thickness: ≥ 5 mm.
  • Maximum test surface area: 40 cm².
  • Magnetism: blocks shall be free of magnetism (steel blocks recommended to be demagnetized before calibration).
  • Flatness and parallelism: flatness deviation ≤ 0.005 mm; parallelism error ≤ 0.010 mm per 50 mm.
  • Surface roughness: Ra ≤ 0.05 µm; surface free of scratches that interfere with indentation measurement.
  • Marking: thickness recorded to the nearest 0.01 mm or an identifying mark on the test surface to prevent regrind.
• Calibration machine and verification
  • Must meet ISO 4545‑2 general requirements plus additional checks in this part.
  • Direct verification interval: not exceeding 12 months.
  • Direct verification includes: calibration of test force, indenter verification, diagonal measurement system calibration/verification, and verification of the testing cycle (or force vs. time behavior).
  • Instruments used for verification must be traceable to national standards.
  • Test force verification performed at three plunger positions (covering travel limits).
• Uniformity and uncertainty
  • Procedures and acceptance criteria for uniformity of hardness across the block and for estimating measurement uncertainty (see Annex B).
• Supporting material
  • Annex A: guidance on adjustment of Köhler illumination systems.
  • Annex B: calculation of uncertainty of mean hardness value.
• Documentation
  • Requirements for marking and issuing a calibration certificate and statements on calibration validity.

Applications and users

• Calibration and testing laboratories performing Knoop hardness measurements.
• Quality assurance teams in metallurgy, aerospace, automotive and precision manufacturing.
• Manufacturers of hardness testers and reference blocks.
• Accreditation bodies and calibration service providers ensuring traceability, repeatability and compliance with ISO standards.

Related standards

• ISO 4545-1: Knoop test method
• ISO 4545-2: Verification and calibration of testing machines
• ISO 376: Calibration of force‑proving instruments

Keywords: EN ISO 4545-3:2018, Knoop hardness, calibration, reference blocks, hardness testing, metallic materials, traceability, uncertainty, ISO 4545-2.