Overview
ISO/TS 17865:2016 provides guidelines for evaluating CMM test value uncertainty for coordinate measuring machines (CMMs) that use single and multiple stylus contacting probing systems. It is a Geometrical Product Specification (GPS) technical specification intended to be applied when testing under ISO 10360‑5. The document explains which uncertainty contributors to consider, gives recommended formulae for standard uncertainties of probing form, size and location, and describes practical measurement checks (fixturing, stem bending, sphere form).
Keywords: ISO/TS 17865:2016, CMM test uncertainty, ISO 10360‑5, probing systems, GPS
Key topics and technical requirements
- Scope and purpose: Guidance to evaluate the test value uncertainty (used to reduce the acceptance zone in tests) distinct from measurement uncertainty.
- Main uncertainty contributors:
- Fixturing and bending of the test sphere stem - assess displacement under probing force (d_FIXTURING) using a displacement sensor or by comparing different probing forces.
- Form of the test sphere - use calibrated form (sphericity) and its uncertainty; if only roundness is available, Annex A provides guidance for approximate conversion (buyer/seller agreement required).
- Probing system errors - recommended formulae are provided for the standard uncertainty of:
- probing system form error
- probing system size (diameter) error
- probing system location error
- Statistical considerations: The document notes the one-sided nature of these tests and recommends a coverage factor k = 1.645 to approximate a 95% confidence level for one-sided distributions (instead of the usual k = 2).
- Practical measurement methods: Use calibrated artefacts (spheres), displacement sensors, and documented calibration certificates (including reported expanded uncertainty U and coverage factor k) to derive standard uncertainties.
Practical applications and users
Who uses ISO/TS 17865:2016:
- Metrology laboratories performing CMM acceptance and reverification tests under ISO 10360‑5.
- Quality engineers and inspection specialists who need to quantify test value uncertainty for contact probing on parts.
- Manufacturers and suppliers of CMMs and probing systems for compliance demonstrations.
- Contracting parties (buyer/seller) who must agree on acceptable approaches when ideal calibration data are not available (e.g., roundness vs form).
Practical benefits:
- Improves consistency and defensibility of CMM test decisions.
- Helps identify dominant uncertainty sources (fixturing, probe force, sphere form) and prioritize mitigation.
- Supports traceable reporting using calibration certificates and GUM-based uncertainty treatment.
Related standards
- ISO 10360‑5 - Acceptance and reverification tests for CMMs using contacting probes (normative link).
- ISO/TS 23165 - General guidance on CMM test uncertainty.
- ISO 14253‑1, ISO 17450‑2, GUM (ISO/IEC Guide 98‑3) and VIM (ISO/IEC Guide 99) - relevant GPS and uncertainty frameworks.
For reliable application, users should read ISO/TS 17865:2016 together with ISO 10360‑5 and supporting GPS documents to ensure correct interpretation and traceability.