Overview
ISO 48-9:2018 - "Rubber, vulcanized or thermoplastic - Determination of hardness - Part 9: Calibration and verification of hardness testers" specifies procedures to calibrate and verify durometers and IRHD/VLRH hardness testers used for rubber and thermoplastic hardness measurement. The standard covers durometer types A, D, AO, AM, IRHD pocket meters, IRHD dead‑load instruments, and dead‑load instruments using the very low rubber hardness (VLRH) scale. It provides metrological requirements, environmental conditions and step‑by‑step methods to ensure accurate, traceable hardness readings.
Key Topics and Technical Requirements
- Scope and instruments: Procedures for durometers (A, D, AO, AM), IRHD pocket meters, IRHD dead‑load testers and VLRH dead‑load devices.
- Environmental conditions: Calibration/verification room temperature must be 18 °C to 25 °C.
- Metrological requirements: Measurands include indentor geometry, pressure‑foot geometry, indentation depth, contact and total forces, spring force and timing. Detailed dimensional and force tolerances are specified for each instrument type (see ISO 48‑9 tables and figures).
- Measurement uncertainty: Measuring instruments used for calibration shall have an uncertainty not greater than 0.2 times the tolerances specified in the standard.
- Calibration methods: Use of coordinate‑measuring devices, measuring microscopes or profile projectors for indentor geometry; verified procedures for depth of indentation, mass/force on pressure foot, spring force and force durations.
- Timing requirements: Typical durations include 3 s or 15 s for durometers and specific durations (e.g., 5 s pre‑force, 30 s indenting) for IRHD/VLRH methods.
- Documentation: Requirements for a calibration and verification certificate are included to support traceability and conformity.
Applications and Users
ISO 48-9:2018 is essential for:
- Testing and calibration laboratories performing rubber hardness calibration and seeking traceable results.
- Quality‑control teams in rubber, tyre, seal, hose and thermoplastic manufacturing to ensure consistent hardness measurements.
- Instrument manufacturers of durometers and IRHD devices to verify product conformity.
- Accreditation bodies and personnel implementing ISO/IEC 17025 requirements for competence of testing and calibration labs.
Practical benefits include improved measurement accuracy, reduced inter‑laboratory variability, and documented traceability for hardness testing used in product specifications, R&D and compliance.
Related Standards (if applicable)
Keywords: ISO 48-9:2018, rubber hardness, durometer calibration, IRHD, VLRH, hardness testers, calibration and verification, metrological requirements, hardness testing.