ISO 1938-1:2015

Overview

ISO 1938-1:2015 - Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1: Plain limit gauges of linear size - specifies the metrological and design characteristics for plain limit gauges used to verify linear sizes (features of size) up to 500 mm. The standard defines gauge types (GO/NO GO, single or double elements), the Maximum Permissible Limits (MPLs) for new and wear states, and describes how to use plain limit gauges for verification of dimensional specifications in accordance with GPS principles.

Key topics and requirements

• Scope and definitions: Terminology for limits (ULS, LLS, MMLS, LMLS), gauge types and functions in the GPS context.
• Gauge types covered: Full-form and segmental plug/bar/spherical types and special forms - e.g. gauge types A–K (full form cylindrical plug, segmental cylindrical bar, spherical plug, bar gauge, rod gauge with spherical ends, full form ring, notch and gap gauges).
• Design characteristics: Mechanical and geometric design aspects required to simulate perfect contacting features for internal and external measurements.
• Metrological characteristics: Parameters and measurement properties that must be defined and controlled for each plain limit gauge, including criteria tied to GO/NO GO function.
• Maximum Permissible Limits (MPLs): Specified MPLs for new-state and wear-state conditions for key metrological characteristics.
• Use and verification: Procedures for proving conformance of gauges, verifying workpiece dimensional specifications with limit gauging, and marking requirements.
• Supporting guidance: Informative annexes on general principles and application of limit gauging, uncertainty considerations, and relation to the GPS matrix model.

Practical applications and users

ISO 1938-1:2015 is directly applicable to:

• Quality and inspection engineers implementing GO/NO GO checks for production parts.
• Metrologists and calibration laboratories specifying MPLs and validating plain limit gauges.
• Toolmakers and gauge designers producing plain limit gauges for internal/external features.
• Manufacturing engineers and inspection technicians using limit gauging for fast, repeatable acceptance testing on rigid workpieces.

Typical applications include acceptance checks of shafts, bores, and flat features where rapid verification against upper/lower specification limits is required.

Related standards

ISO 1938-1:2015 is part of the GPS family and references (among others):

• ISO 286-1:2010 (tolerances on linear sizes)
• ISO 1101:2012, ISO 14405-1:2010
• ISO 14253-1/2:2013/2011 (decision rules, uncertainty guidance)
• ISO 17450-1/2, ISO/IEC Guide 98-3 (GUM), ISO/IEC Guide 99 (VIM)

By aligning gauge design, use and conformity assessment with ISO 1938-1:2015, organizations ensure consistent, traceable limit gauging practices within the GPS framework.