Overview
EN ISO 12180-1:2011 - "Geometrical product specifications (GPS) - Cylindricity - Part 1: Vocabulary and parameters of cylindrical form" is a CEN-endorsed ISO standard that establishes the vocabulary, concepts and parameters used to describe cylindricity for individual complete integral features (right circular cylinders). It defines how cylindricity is represented, which reference cylinders are used, and which parameters (for example peak-to-valley deviations) quantify deviations from ideal cylindrical form.
Key topics
- Scope and focus: Terminology and parameters for cylindricity of individual integral features only (not assemblies or derived features).
- Extracted surfaces and lines: Definitions for the digital representation of the real surface (extracted surface) and generatrix (extracted generatrix line) used for evaluation.
- Reference cylinders: Clear definitions of reference-element conventions, including:
- Minimum zone (MZ) - two coaxial cylinders with least radial separation
- Least squares (LS) - cylinder minimizing sum of squared deviations
- Minimum circumscribed (MC) and Maximum inscribed (MI)
- Local deviations and parameters:
- Local cylindricity deviation (radial deviation normal to the reference cylinder)
- Peak-to-valley cylindricity deviation (largest positive plus largest negative local deviation)
- Generatrix-related terms (generatrix profile, generatrix wavelength)
- Relation to radial cross-section and straightness deviations
- Data extraction and filtering: The standard emphasizes that the choice of data extraction and filters (Gaussian, spline, wavelet, morphological, etc.) affects the cylindricity definition and must be specified unambiguously. It does not restrict measurement methods.
- Relationship to GPS framework: Part 1 supplies vocabulary and parameters; specification operators are addressed in ISO 12180-2. It references related GPS standards (roundness, straightness, surface texture and general GPS model).
Applications and users
EN ISO 12180-1:2011 is used where accurate definition and measurement of cylindrical form are required:
- Quality and metrology engineers defining acceptance criteria for shafts, bores, pins, sleeves and bearing journals
- Manufacturing and process engineers setting machinability and inspection requirements
- CMM programmers and inspection labs implementing measurement routines and reporting cylindricity results
- Designers and drawing authors specifying form tolerances within the GPS/GD&T system
- Standards writers and auditors ensuring consistent terminology across specifications
Practical use cases include defining measurement procedures on CMMs, selecting the appropriate reference cylinder method for contract inspection, and ensuring unambiguous specification of filters and extraction conventions for traceable verification.
Related standards
Keywords: EN ISO 12180-1:2011, cylindricity, GPS, cylindrical form, reference cylinder, minimum zone, least squares, peak-to-valley deviation, CMM measurement, surface extraction, filter.