Overview - ISO/TR 27609:2007 (Vibration measurement for grinders)
ISO/TR 27609:2007 is a Technical Report that evaluates a round‑robin test of vibration measurement methods for hand‑held grinders. The work aimed to identify a repeatable test procedure that satisfies the requirement in ISO 20643 for measuring vibration emissions in three directions, supporting the planned revision of ISO 8662‑4 (hand‑held grinders). The report compares two methods - a redesigned unbalance disc test and a real grinding test - and analyses repeatability, reproducibility and correlation with real‑use vibration.
Key topics and technical requirements
- Purpose: establish a test method that represents the upper quartile of vibration likely in typical real use (i.e., declared values reflect higher-end normal working conditions).
- Measurement directions: three‑axis (x, y, z), frequency‑massed rms acceleration values (per ISO 20643 terminology).
- Evaluated methods:
- Unbalance disc test: a depressed‑centre disc with a movable unbalance screw (tight tolerances) was used to simulate wheel unbalance. Tests used a reference disc (RD) and locally made disc (LD). Feed force followed ISO 8662‑4:1994 recommendations.
- Grinding test: real grinding on mild steel with type 27 depressed‑centre wheels; test sequence used 10 s no‑load, 1 min grinding, then 10 s no‑load, with five wheels per grinder and one run per wheel.
- Statistical evaluation: spread between operators, spread between laboratories (reproducibility), repeatability, and correlation between no‑load (unbalance) and grinding vibration levels were analysed. Significance testing used 95% t‑tests.
Practical applications and who uses this standard
- Intended users:
- Test laboratories and calibration facilities performing vibration emission measurements.
- Tool manufacturers designing, testing and declaring vibration emissions for grinders.
- Occupational health & safety authorities and ergonomics specialists assessing exposure to hand‑arm vibration.
- Standards committees and conformity assessors aligning ISO 8662‑4 with ISO 20643 requirements.
- Practical takeaways:
- The unbalance disc method is suitable for estimating real‑use vibration values for grinders without auto‑balancing units.
- The unbalance test underestimates real‑use vibration for grinders fitted with auto‑balancing units; methods for those units are not covered.
- The real grinding test showed large spread between results and is not suitable for producing a declared vibration value (high variability and time‑consuming).
Related standards
- ISO 20643 - Vibration measurement / declared values for power tools (three‑direction requirement)
- ISO 8662‑4 - Hand‑held grinders (planned revision context)
Keywords: ISO/TR 27609:2007, vibration measurement, hand‑held grinders, unbalance disc, grinding test, ISO 20643, ISO 8662‑4, round‑robin test, vibration emissions, repeatability, reproducibility.
Open preview (PDF)Vibration in hand-held tools — Vibration measurement methods for grinders — Evaluation of round-robin test