EN ISO 1938-1:2015

Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1: Plain limit gauges of linear size (ISO 1938-1:2015)

ISO 1938-1:2015 specifies the most important metrological and design characteristics of plain limit gauges of linear size.
ISO 1938-1:2015 defines the different types of plain limit gauges used to verify linear dimensional specifications associated with linear size.
ISO 1938-1:2015 also defines the design characteristics and the metrological characteristics for these limit gauges as well as the new or wear limits state Maximum Permissible Limits (MPLs) for the new state or wear limits state for these metrological characteristics.
In addition, ISO 1938-1:2015 describes the use of limit gauges. It covers linear sizes up to 500 mm.

Geometrische Produktspezifikation (GPS) - Längenprüftechnik - Teil 1: Grenzlehren und Lehrung der Längenmaße (ISO 1938-1:2015)

Diese Internationale Norm legt die wichtigsten messtechnischen Merkmale und Konstruktionsmerkmale für
glatte Grenzlehren der linearen Größenmaße fest.
Diese Internationale Norm definiert die verschiedenen Arten von glatten Grenzlehren, die für den Nachweis
der Übereinstimmung mit Maßspezifikationen für lineare Größenmaße angewendet werden.
Diese Internationale Norm legt ebenfalls die Konstruktionsmerkmale und messtechnischen Merkmale für
diese Grenzlehren sowie die Grenzwerte für Messabweichungen (MPEs) für Lehren im Neuzustand oder
Verschleißzustand für diese Merkmale fest.
Diese Internationale Norm beschreibt weiterhin die Anwendung von Grenzlehren und deckt lineare
Größenmaße bis zu 500 mm ab.

Spécification géométrique des produits (GPS) - Équipement de mesure dimensionnel - Partie 1: Calibres lisses à limite de taille linéaire (ISO 1938-1:2015)

ISO 1938-1:2015 spécifie les caractéristiques métrologiques et de conception les plus importantes des calibres lisses à limites de taille linéaire.
ISO 1938-1:2015 définit les différents types de calibres lisses à limites utilisés pour vérifier les spécifications dimensionnelles linéaires associées à la taille linéaire.
ISO 1938-1:2015 définit également les caractéristiques de conception et les caractéristiques métrologiques de ces calibres à limites, ainsi que l'état neuf ou l'état limite d'usure des limites maximales tolérées (Maximum Permissible Limits, MPL) de l'état neuf ou de l'état limite d'usure de ces caractéristiques métrologiques.
ISO 1938-1:2015 décrit également l'utilisation des calibres à limites. Elle couvre les tailles linéaires jusqu'à 500 mm.

Specifikacija geometrijskih veličin izdelka (GPS) - Oprema za merjenje dimenzij - 1. del: Ploščati mejni merilniki linearne velikosti (ISO 1938-1:2015)

Ta mednarodni standard določa najpomembnejše meroslovne in oblikovne značilnosti ploščatih mejnih merilnikov linearne velikosti. Ta mednarodni standard določa različne vrste ploščatih mejnih merilnikov, ki se uporabljajo za dokazovanje skladnosti z linearno specifikacijo mer, povezano z linearno velikostjo.
Ta mednarodni standard določa tudi oblikovne in meroslovne značilnosti teh mejnih merilnikov ter MPE pri novem ali izrabljenem stanju za te značilnosti.
Ta mednarodni standard opisuje tudi uporabo mejnih merilnikov in pokriva linearne velikosti do 500 mm.

General Information

• Status: Published
• Publication Date: 17-Nov-2015
• Withdrawal Date: 30-May-2016
• ICS: 17.040.10 - Limits and fits
• ICS: 17.040.30 - Measuring instruments
• Technical Committee: CEN/TC 290 - Dimensional and geometrical product specification and verification
• Drafting Committee: CEN/TC 290 - Dimensional and geometrical product specification and verification
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 18-Nov-2015
• Completion Date: 18-Nov-2015
• Ref Project: SIST EN ISO 1938-1:2016 - Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1: Plain limit gauges of linear size (ISO 1938-1:2015)

Relations

• Revised: prEN ISO 1938-1 - Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1: Plain limit gauges of linear size (ISO/DIS 1938-1:2025)
• Effective Date: 04-Oct-2023

Overview

EN ISO 1938-1:2015 - Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1: Plain limit gauges of linear size - specifies the principal metrological and design characteristics for plain limit gauges (GO/NO GO style) used to verify linear sizes. The standard defines gauge types, their intended use, and the Maximum Permissible Limits (MPLs) for new and wear states. It applies to linear sizes up to 500 mm and forms part of the ISO/GPS system for dimensional measurement and verification.

Keywords: EN ISO 1938-1:2015, plain limit gauges, linear size, GPS, dimensional measuring equipment, MPLs, limit gauges, verification

Key Topics

• Scope and definitions: Terms and limits related to features of size (ULS, LLS, MMLS, LMLS) and gauge classifications.
• Gauge types: Identification and purpose of different plain limit gauges used for verifying linear dimensional specifications.
• Design characteristics: Requirements for physical and functional design that ensure repeatable and reliable gauging.
• Metrological characteristics: Specifications for measurement behavior, uncertainty considerations and how these characteristics vary with gauge type (e.g., GO or NO GO).
• MPLs (Maximum Permissible Limits): Definition and application of MPLs for both new and wear limits states of gauges.
• Use and verification: Guidance on proving conformance of gauges, applying limit gauges to workpiece inspection, and decision rules for conformity.
• Marking and documentation: Requirements for gauge identification and traceability.
• Informative annexes: Practical principles and application guidance, uncertainty aspects for various gauge types, and relation to the GPS matrix model.

Applications

EN ISO 1938-1:2015 is practical for professionals and organizations involved in dimensional inspection and gauge production:

• Quality assurance and inspection teams using GO/NO GO limit gauges on production lines
• Calibration laboratories and metrology labs establishing metrological characteristics and MPLs
• Gauge designers and manufacturers creating plain limit gauges for linear sizes up to 500 mm
• Manufacturing engineers and production supervisors implementing in-line verification for parts with linear size tolerances
• Standards and compliance officers aligning inspection procedures with GPS decision rules

Practical benefits include standardized gauge design and performance expectations, clearer traceability, consistent verification practices, and reduced measurement uncertainty when using limit gauges.

Related Standards

This part of ISO 1938 references and complements other GPS and metrology standards, including:

• ISO 286-1 (tolerances on linear sizes)
• ISO 1101 (geometrical tolerancing)
• ISO 14405-1 (linear sizes)
• ISO 14253-1 / ISO 14253-2 (inspection decision rules and uncertainty)
• ISO 17450-1 / ISO 17450-2 (GPS general concepts)
• ISO/IEC Guide 98-3 (GUM) and ISO/IEC Guide 99 (VIM)

See also ISO 1938‑2 for related reference disk gauges.

Standards Content (Sample)

SLOVENSKI STANDARD
01-februar-2016
6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND*362SUHPD]DPHUMHQMHGLPHQ]LM
GHO3ORãþDWLPHMQLPHULOQLNLOLQHDUQHYHOLNRVWL,62
Geometrical product specifications (GPS) - Dimensional measuring equipment - Part 1:
Plain limit gauges of linear size (ISO 1938-1:2015)
Geometrische Produktspezifikation (GPS) - Maßtolerierung - Teil 1: Grenzlehren und
Lehrung der Längenmaße (ISO 1938-1:2015)
Spécification géométrique des produits (GPS) - Équipement de mesure dimensionnel -
Partie 1: Calibres lisses à limite de taille linéaire (ISO 1938-1:2015)
Ta slovenski standard je istoveten z: EN ISO 1938-1:2015
ICS:
17.040.30 Merila Measuring instruments
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND*36 Specification (GPS)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 1938-1
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2015
EUROPÄISCHE NORM
ICS 17.040.10
English Version
Geometrical product specifications (GPS) - Dimensional
measuring equipment - Part 1: Plain limit gauges of linear
size (ISO 1938-1:2015)
Spécification géométrique des produits (GPS) - Geometrische Produktspezifikation (GPS) -
Équipement de mesure dimensionnel - Partie 1: Maßtolerierung - Teil 1: Grenzlehren und Lehrung der
Calibres lisses à limite de taille linéaire (ISO 1938- Längenmaße (ISO 1938-1:2015)
1:2015)
This European Standard was approved by CEN on 27 April 2015.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 1938-1:2015 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 1938-1:2015) has been prepared by Technical Committee ISO/TC 213
"Dimensional and geometrical product specifications and verification" in collaboration with Technical
Committee CEN/TC 290 “Dimensional and geometrical product specification and verification” the
secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2016, and conflicting national standards shall be
withdrawn at the latest by May 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 1938-1:2015 has been approved by CEN as EN ISO 1938-1:2015 without any
modification.
INTERNATIONAL ISO
STANDARD 1938-1
First edition
2015-11-01
Geometrical product specifications
(GPS) — Dimensional measuring
equipment —
Part 1:
Plain limit gauges of linear size
Spécification géométrique des produits (GPS) — Équipement de
mesure dimensionnel —
Partie 1: Calibres lisses à limite de taille linéaire
Reference number
ISO 1938-1:2015(E)
©
ISO 2015
ISO 1938-1:2015(E)
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
3.1 Limits . 2
3.2 Gauge types . 3
3.3 Characteristics and function of gauges . 6
4 Abbreviated terms and symbols . 7
5 Design characteristics for gauges . 8
6 Metrological characteristics .10
6.1 General .10
6.2 Metrological characteristic relative to the type of limit gauge (GO gauge or
NO GO gauge) .10
7 Maximum permissible limits on metrological characteristics .14
7.1 General .14
7.2 Limit gauges for internal features of size .15
7.3 Limit gauges for external features of size .16
7.4 Values for calculation of MPL of limit gauges .18
8 Proving conformance with specification for limit gauges .21
9 Verification of dimensional specification of a workpiece with limit gauges .21
10 Marking .23
Annex A (informative) General principles and application of limit gauging .24
Annex B (informative) Description of the specific use of the various gauge types and the
associated uncertainty .26
Annex C (informative) Relation to the GPS matrix model .28
Bibliography .30
ISO 1938-1:2015(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 213, Geometrical product specifications and
verification.
This first edition cancels and replaces ISO/R 1938:1971, which has been technically revised.
ISO 1938 consists of the following parts, under the general title Geometrical product specifications
(GPS) — Dimensional measuring equipment:
— Part 1: Plain limit gauges of linear size
— Part 2: Reference disk gauges
This part of ISO 1938 does not include requirements for setting plug gauges and setting ring gauges,
which were dealt with in ISO/R 1938:1971, 3.9.4.
This part of ISO 1938 covers the concepts and principles developed in ISO 14978.
iv © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Introduction
This part of ISO 1938 is a geometrical product specification (GPS) standard and is to be regarded as a
general GPS standard (see ISO 14638). It influences chain links E, F and G of the size chain of standards
in the general GPS matrix. For more detailed information of the relation of this part of ISO 1938 to other
standards and the GPS matrix model, see Annex C.
The ISO/GPS matrix model given in ISO 14638 gives an overview of the ISO/GPS system of which this
document is a part. The fundamental rules of ISO/GPS given in ISO 8015 apply to this document and
the default decision rules given in ISO 14253-1 apply to specifications made in accordance with this
document, unless otherwise indicated.
The terms and concepts used in this first edition of ISO 1938-1 (compared to the former edition
ISO/R 1938:1971) have been changed according to needs and terminology in the other GPS standards.
This part of ISO 1938 deals with verification, using plain limit gauges, of linear sizes for features of size
when the dimensional specifications are required (see ISO 14405-1), for rigid workpieces.
NOTE Tables 4 and 5 use the modifiers given in ISO 14405-1 and ISO 1101.
INTERNATIONAL STANDARD ISO 1938-1:2015(E)
Geometrical product specifications (GPS) — Dimensional
measuring equipment —
Part 1:
Plain limit gauges of linear size
1 Scope
This part of ISO 1938 specifies the most important metrological and design characteristics of plain
limit gauges of linear size.
This part of ISO 1938 defines the different types of plain limit gauges used to verify linear dimensional
specifications associated with linear size.
This part of ISO 1938 also defines the design characteristics and the metrological characteristics for
these limit gauges as well as the new or wear limits state Maximum Permissible Limits (MPLs) for the
new state or wear limits state for these metrological characteristics.
In addition, this part of ISO 1938 describes the use of limit gauges. It covers linear sizes up to 500 mm.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 286-1:2010, Geometrical product specifications (GPS) — ISO code system for tolerances on linear
sizes — Part 1: Basis of tolerances, deviations and fits
ISO 1101:2012, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,
orientation, location and run-out
ISO 14405-1:2010, Geometrical product specifications (GPS) — Dimensional tolerancing — Part 1: Linear
sizes
ISO 14253-1:2013, Geometrical product specifications (GPS) — Inspection by measurement of workpieces
and measuring equipment — Part 1: Decision rules for proving conformity or nonconformity with
specifications
ISO 14253-2:2011, Geometrical product specifications (GPS) — Inspection by measurement of workpieces
and measuring equipment — Part 2: Guidance for the estimation of uncertainty in GPS measurement, in
calibration of measuring equipment and in product verification
ISO 17450-1:2011, Geometrical product specifications (GPS) — General concepts — Part 1: Model for
geometrical specification and verification
ISO 17450-2:2012, Geometrical product specifications (GPS) — General concepts — Part 2: Basic tenets,
specifications, operators, uncertainties and ambiguities
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
ISO 1938-1:2015(E)
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 286-1, ISO 14405-1, ISO 17450-2,
ISO/IEC Guide 98-3 and ISO/IEC Guide 99 and the following definitions apply.
3.1 Limits
3.1.1
maximum material limit of size
MMLS
limit of size corresponding to the maximum material condition of feature of size
Note 1 to entry: MMLS includes the numerical value for the size and the specified association criteria.
Note 2 to entry: A number of different association criteria for size are given in ISO 14660-2 and ISO 14405-1.
3.1.2
least material limit of size
LMLS
limit of size corresponding to the least material condition of feature of size
Note 1 to entry: LMLS includes the numerical value for the size and the specified association criteria.
Note 2 to entry: A number of different association criteria for size are given in ISO 14660-2 and ISO 14405-1.
3.1.3
upper limit of size
ULS
largest permissible size of a feature of size
Note 1 to entry: ULS is a numerical value.
[SOURCE: ISO 286-1:2010, 3.2.3.1]
3.1.4
lower limit of size
LLS
smallest permissible size of a feature of size
Note 1 to entry: LLS is a numerical value.
[SOURCE: ISO 286-1:2010, 3.2.3.2]
3.1.5
upper specification limit
USL
limit of a specification for a metrological characteristic of a gauge having the largest value
3.1.6
lower specification limit
LSL
limit of a specification for a metrological characteristic of a gauge having the smallest value
2 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
3.2 Gauge types
3.2.1
limit gauge
gauge designed and intended to verify only if workpiece characteristics are inside or outside the
tolerance at one of its tolerance limits
Note 1 to entry: When a limit gauge is designed to verify an internal feature of size (a hole for example), then it
can be called internal limit gauge.
Note 2 to entry: When a limit gauge is designed to verify an external feature of size (a shaft for example), then it
can be called external limit gauge.
Note 3 to entry: General application of limit gauge is given in Annex A.
Note 4 to entry: A limit gauge may be physical or virtual.
3.2.2
plain limit gauge
physical limit gauge with only one or two gauge elements, each one simulating a perfect feature of size,
whose size is derived from upper or lower specification limits of the size of a feature of size
Note 1 to entry: When a plain limit gauge consists of only one element, it is qualified as simple (simple plain limit
gauge: GO plain limit gauge or NO GO plain limit gauge).
Note 2 to entry: When a plain limit gauge consists of two elements, it is qualified as double (double plain limit
gauge: GO and NO GO).
3.2.3
full form cylindrical plug gauge
gauge type A
plain limit gauge designed to simulate a cylinder as a contacting feature with an internal cylinder
Note 1 to entry: See Table 1.
Note 2 to entry: The GO gauge type A simulates a dimensional specification defining the maximum material limit
of size with the envelope requirement when the gauge length is greater or at least equal to the length of the
feature of size of the workpiece.
3.2.4
segmental cylindrical bar gauge
gauge type B
plain limit gauge designed to simulate two opposite angular portions of a cylinder as a contacting
feature with an internal cylinder
Note 1 to entry: See Table 1.
3.2.5
segmental cylindrical bar gauge with reduced gauging surfaces
gauge type C
segmental cylindrical bar gauge designed to simulate two reduced opposite angular portions of a
cylinder as a contacting surface with an internal cylinder
Note 1 to entry: See Table 1.
3.2.6
full form spherical plug gauge
gauge type D
plain limit gauge designed to simulate a circle as a contacting feature with an internal cylinder
Note 1 to entry: See Table 1.
ISO 1938-1:2015(E)
Note 2 to entry: The shape of this gauge type is not spherical, but a torus - per tradition the name is “spherical
plug gauge”.
3.2.7
segmental spherical plug gauge
gauge type E
plain limit gauge designed to simulate two opposite angular portions of a circle as a contacting feature
with an internal cylinder
Note 1 to entry: See Table 1.
Note 2 to entry: The shape of this gauge type is not spherical but a torus - per tradition the name is “segmental
spherical plug gauge”.
3.2.8
bar gauge
gauge type F
full form bar gauge
plain limit gauge designed to simulate two opposite planes as a contacting feature with an internal
feature of size consisting of two opposite planes
Note 1 to entry: See Table 1.
3.2.9
rod gauge with spherical ends
gauge type G
plain limit gauge designed to simulate two opposite points as a contacting feature with an internal
feature of size consisting of two opposite planes or of a cylinder
Note 1 to entry: See Table 1.
Note 2 to entry: The active part of a rod gauge with spherical ends consists only of two points: the two points at
the largest distance between the two spheres.
Table 1 — Types of limit gauge for internal feature of size
Nominal con-
Nominal con-
tacting feature
tacting feature
with feature of
Limit gauge Type Illustration with feature
size of type “two
of size of “type
opposite paral-
Cylinder”
lel planes”
Two opposite par-
Full form cylindrical plug gauge Gauge type A Cylinder
allel straight lines
Two opposite
Two opposite par-
Segmental cylindrical bar gauge Gauge type B angular portions
allel straight lines
of cylinder
Two opposite
Segmental cylindrical bar gauge with angular reduced Two opposite par-
Gauge type C
reduced gauging surfaces portions of cyl- allel line segments
inder
4 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Table 1 (continued)
Nominal con-
Nominal con-
tacting feature
tacting feature
with feature of
Limit gauge Type Illustration with feature
size of type “two
of size of “type
opposite paral-
Cylinder”
lel planes”
Full form spherical plug gauge Gauge type D Circle Two points
Two opposite
Segmental spherical plug gauge Gauge type E angular portions Two points
of circle
Two opposite par-
Bar gauge Gauge type F Not applicable
allel planes
Rod gauge with spherical ends Gauge type G Two points Two points
3.2.10
full form cylindrical ring gauge
gauge type H
plain limit gauge designed to simulate a cylinder as contacting feature with an external cylinder
Note 1 to entry: See Table 2.
3.2.11
full form notch gauge
gauge type J
plain limit gauge designed to simulate straight lines or flat surfaces on two opposite parallel planes as
contacting features with an external feature of size consisting of a cylinder or two opposite planes
Note 1 to entry: See Table 2.
3.2.12
gap gauge
gauge type K
plain limit gauge designed to simulate portions (straight lines or flat surfaces) on two opposite planes
as contacting feature with an external feature of size consisting of a cylinder or two opposite planes
Note 1 to entry: See Table 2.
ISO 1938-1:2015(E)
Table 2 — Types of limit gauge for external feature of size
Nominal contacting feature with fea-
ture of size of type:
Limit gauge Type Illustration
“two opposite parallel
“cylinder”
planes”
Full form cylindrical ring gauge Gauge type H Cylinder Not applicable
Two oppo-
site parallel Two opposite parallel
Full form notch gauge Gauge type J
straight planes
lines
Two oppo-
site parallel Two opposite parallel por-
Gap gauge Gauge type K
straight line tions of planes
segments
3.3 Characteristics and function of gauges
3.3.1
non-adjustable gauge
gauge with an inherent, stable and not changeable nominal metrological characteristic
Note 1 to entry: The metrological characteristics of a non-adjustable gauge may change with e.g. temperature
and wear.
EXAMPLE A full form cylindrical plug gauge and a full form cylindrical ring gauge are non-adjustable gauges.
3.3.2
adjustable gauge
gauge designed in a way that the inherent nominal metrological characteristic can be intentionally
changed by the user
Note 1 to entry: The metrological characteristics of an adjustable gauge may also change with e.g.
temperature and wear.
EXAMPLE A variable gap gauge and a variable rod gauge with spherical ends are adjustable gauges.
3.3.3
GO gauge
gauge designed to verify the size of the workpiece relative to maximum material size according to
dimensional specification
Note 1 to entry: Usually relative to the maximum material limit of size (MMLS) of the dimensional specification,
the GO gauge passing over the actual feature of size of the workpiece, defines an acceptance and the GO gauge,
not passing over the actual feature of size of the workpiece defines a non-acceptance.
3.3.4
NO GO gauge
gauge designed to verify the size of the workpiece relative to least material size according to dimensional
specification
Note 1 to entry: Usually relative to the least material limit of size (LMLS) of the dimensional specification, the
NO GO gauge not passing over the actual feature of size of the workpiece defines an acceptance and the NO GO
gauge passing over the actual feature of size of the workpiece defines a non-acceptance.
6 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
3.3.5
length of gauge element
active length of a gauge in the direction perpendicular to a cross section of the gauged feature of size
Note 1 to entry: For a cylindrical gauge element, it is the length of the cylinder (see Table 4). For a gauge element
of type “two parallel opposite surfaces”, it is the length of the bar or notch (see Table 4). For a gap gauge, it is the
width of the anvils (see Table 4).
3.3.6
height of gauge element
active height of a gauge in the direction parallel to a cross section of the gauged feature of size
Note 1 to entry: For a gauge element of type two parallel opposite surfaces, it is the height of the bar or notch (see
Table 4). For a gap gauge, it is the height of the anvils (see Table 4).
3.3.7
new state specification
specification for metrological characteristics of a new gauge to be used by a
manufacturer or supplier
3.3.8
wear limits state specification
specification for metrological characteristics of a used gauge
Note 1 to entry: The user may use standardized wear limits state specifications, e.g. as given in this part of ISO 1938.
Note 2 to entry: The wear limits state specifications consider the gauge as used, and can include wear limits.
3.3.9
new state permissible limits of a metrological characteristic
permissible limits of a metrological characteristic in a new state specification
3.3.10
wear limits state permissible limits of a metrological characteristic
permissible limits of a metrological characteristic in a wear limits state specification
4 Abbreviated terms and symbols
For the purpose of this document, the abbreviated terms and symbols given in Table 3 apply.
ISO 1938-1:2015(E)
Table 3 — Abbreviated terms and symbols
Description
Abbreviated term
B width of segmental gauge element
F tolerance value of form specification on limit gauge
GO go gauge
H interval tolerance on the size characteristic, S, for a limit gauge in the new state
LT length of gauge element
HG height of gauge element
USL upper specification limit (of a gauge)
LG length of gauge element
LSL lower specification limit (of a gauge)
LMLS least material limit of size
M new state gauge
MMLS maximum material limit of size
MPL maximum permissible limits of a metrological characteristic
NO GO no go gauge
S size
SR spherical radius of the gauge
T tolerance
U wear limits state gauge
W workpiece
Symbol
y amount outside of workpiece tolerance limit taking into account a margin of wear limit
for internal feature of size
y amount outside of workpiece tolerance limit taking into account a margin of wear limit
for external feature of size
z distance between centre of tolerance for GO new state gauge and the lower specification
limit of an internal feature of size of a workpiece
z distance between centre of tolerance for GO new state gauge and the upper specification
limit of an external feature of size of a workpiece
α safety allowance for measurement uncertainty for internal feature of size
α safety allowance for measurement uncertainty for external feature of size
5 Design characteristics for gauges
The material used for gauges shall be suitably selected with due consideration to its size stability,
durability and stiffness.
Gauging elements shall normally be manufactured from a high quality steel suitably selected to provide a
high degree of wear resistance after heat treatment. Other wear-resistant materials, e.g. tungsten carbide,
may be used provided that their wear qualities are not less than those of the steel specified above.
NOTE The temperature expansion coefficient of the material used is to be considered together with the
wear resistance.
8 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Hard plating or other surface treatments in order to improve the wear resistance of the surface may
also be applied to gauging surfaces, but the thickness of deposit shall at least be of an amount, that an
acceptable gauge always has a fully intact layer of wear resistant material.
The hardness of the gauging surface shall not be less than 670 HV 30 (approximately 58 HRC),
irrespective of the type of material.
There may be specific applications where the use of special materials (e.g. aluminium and glass) is
required by the nature of the workpiece or the manufacturing environment. In such cases it may not be
possible to have the required hardness or wear resistance.
The gauging surface shall be finished by fine grinding or lapping or a process which results in a smooth
type of surface. The surface roughness of gauging surface shall be specified and the R value shall not
a
exceed 10 % of the new state gauge MPL for size (see Example and Table 6) with a upper limit value of
0,2 µm, and cut-off value of 0,8 mm (see ISO 1302).
EXAMPLE Surface texture specification related to R parameter on gauging surface:
a
Additional surface texture parameters can be specified.
All sharp edges shall be removed unless functionally required.
The design of grip handle of the plain limit gauge shall take into account ergonomic considerations
(e.g. knurling, hexagon shape) and the associated characteristics to the grip handle are also design
characteristics.
Design options on some gauges are possible; these are given below.
— Air slot: for a GO gauge- full form cylindrical plug gauge: this option is intended to verify a blind hole, to
avoid phenomena of compression and suction. This option requires defining the air slot dimensions.
— Precentering/pilot (see Figure 1): for a GO gauge or a NO GO gauge - full form cylindrical plug gauge
and segmental cylindrical bar gauge; this option is intended to facilitate the introduction of the
gauge in the workpiece. This option requires defining the precentering or pilot dimensions.
When a gauge with precentering option is used for a blind hole, an air slot option may be used.
Figure 1 — Illustration of precentering option (example)
Other specific design characteristics, attached to a type of gauge, are described in Tables 4 and 5.
ISO 1938-1:2015(E)
6 Metrological characteristics
6.1 General
A plain limit gauge has one or two gauge elements (GO gauge or NO GO gauge, or GO and NO GO gauge).
Metrological characteristics are defined for these gauge elements. These metrological characteristics
influence the quality of the evaluation made using the gauge.
The most important metrological characteristics for the gauge elements are the size, S, and form, F.
The modifiers defined in ISO 14405-1 and the symbols defined in ISO 1101 can be used to define the
metrological characteristics.
The size can be seen metrologically by different ways. For example, on a cylinder, it is possible to
evaluate the maximum inscribed diameter, the minimum circumscribed diameter, the minimum local
diameter, the maximum local diameter or the least square diameter. Each of them can yield different
result of measurement. For this reason, the metrological characteristic includes this information (by
adding after the size a modifier as defined in ISO 14405-1).
Depending on the use of the plain gauge and its type, the metrological characteristic impacting the
uncertainty of verification can be different, for the same plain gauge.
NOTE When a slot without envelope requirement is checked for its lower limit with a gauge type A, two
parallel lines will be checked which do not exactly correspond to the definition for two-point size. The gauge type
G is the gauge type that follows the definition for two-point size.
This part of ISO 1938 describes potential metrological characteristics available on plain limit gauge.
The final decision to select one or several metrological characteristics is left to the user.
6.2 Metrological characteristic relative to the type of limit gauge (GO gauge or NO GO
gauge)
Tables 4 and 5 give potential metrological characteristics associated to a gauge type, but also
complementary design characteristics as defined in Clause 5. Depending on the need of the user, a set of
these metrological characteristics shall be defined; by default the two point size is required for the size,
S, of the gauge limit and the form deviation also.
Table 4 — List of potential design and metrological characteristics for external gauge type
Description Complemen- Metrological Metrological
tary design character- character-
character- istics for istics for
istics GO gauge NO GO gauge
Full form cylindrical plug gauge — Gauge type A
S GN /0
a
LG
a
a
10 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Table 4 (continued)
Description Complemen- Metrological Metrological
tary design character- character-
character- istics for istics for
istics GO gauge NO GO gauge
Segmental cylindrical bar gauge — Gauge type B
S CT
GX
S GX /0 CT
S GN CT
S /0 CT
GN
LG
a
B
a
a
Segmental cylindrical bar gauge with reduced gauging surfaces —
Gauge type C
S GX CT
S GX /0 CT
S GN CT
LG
S GN /0 CT
a
B
a
LT
a
Full form spherical plug gauge — Gauge type D
S GX /0 CT
S GN /0 S GN /0 CT
R
LT a
a
a
ISO 1938-1:2015(E)
Table 4 (continued)
Description Complemen- Metrological Metrological
tary design character- character-
character- istics for istics for
istics GO gauge NO GO gauge
Segmental spherical plug gauge — Gauge type E
S GX /0 CT S GX /0 CT
B
S /0 CT S /0 CT
GN GN
LT
a a
R
Bar gauge — Gauge type F LG
S S /0
HG
S S /0
a a
S S
Rod gauge with spherical ends — Gauge type G
a a
SR
12 © ISO 2015 – All rights reserved

ISO 1938-1:2015(E)
Table 4 (continued)
a
default metrological characteristics to be considered
maximum inscribed (see ISO 14405-1)
minimum circumscribed (see ISO 14405-1)
circumferential (see ISO 14405-1)
two point size (see ISO 14405-1)
CT common tolerance (see ISO 14405-1)
Table 5 — List of potential design and metrological characteristics for internal gauge type
Description Complemen- Metrological Metrological
tary design characteristics characteristics
characteris- for GO gauge for NO GO gauge
tics
Full form cylindrical ring gauge — Gauge type H
/0
Dy
/0
LG
a
a
a
Full form notch gauge — Gauge type J LG
S S
HG
S S
a
S S
and and
a
default metrological characteristics to be considered
maximum inscribed (see ISO 14405-1)
minimum circumscribed (see ISO 14405-1)
two point size (see ISO 14405-1)
ISO 1938-1:2015(E)
Table 5 (continued)
Description Complemen- Metrological Metrological
tary design characteristics characteristics
characteris- for GO gauge for NO GO gauge
tics
Gap gauge — Gauge type K LG
S S
HG
S S
a a
S S
and and
Constraint condition:
a) normally the dimension HG is vertical compared to the
gravity direction
b) gap gauges shall only be used for rigid workpieces
a
default metrological characteristics to be considered
maximum inscribed (see ISO 14405-1)
minimum circumscribed (see ISO 14405-1)
two point size (see ISO 14405-1)
7 Maximum permissible limits on metrological characteristics
7.1 General
The maximum permissible limits for a gauge are completely equivalent to the specification limits on a
characteristic.
a) The maximum permissible limits on form and orientation characteristics are asymmetrical.
1) The upper limit of MPL on these characteristics is equal to the value of F given in Table 6 and
depending to the type of the gauge.
2) The lower limit of MPL on these characteristics is equal to 0.
3) The evaluation of these characteristics shall be in accordance with ISO 1101 and shall fulfil MPLs.
EXAMPLE 1 A metrological characteristic of cylindricity with its MPLs is equivalent to the following
requirement: . Its meaning is given in ISO 1101.
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ISO 1938-1:2015(E)
b) Specifications for metrological characteristics associated to S to a limit gauge of the same type
used as a GO gauge and as a NO GO gauge are different (see 7.2 and 7.3) and applicable by default to
the two point size .
Specifications for new or wear limits state attached to the metrological characteristics associated to S
to limit gauges are always different for GO gauges and may be equal for NO GO gauges. The new state
specification limits of GO gauges are always positioned inside the workpiece tolerance.
Tables 6 to 11 can be used directly when the tolerance of the dimension of feature of size of workpiece
is given as a code according to ISO 286-1:2010. When the size tolerance is not given as an ISO code, the
standard tolerance grade shall be defined as the standard tolerance grade corresponding to the first
tolerance interval, T, given in Tables 7 to 11, lower than the tolerance interval of the workpiece in the
same range of nominal sizes.
EXAMPLE 2 For a dimensional specification given on the workpiece, by 20 ± 0,02 , the tolerance interval on
the workpiece is equal to 40 µm. In Table 8, in the nominal range in which 20 is included, the lower standardized
tolerance interval is equal to 33 µm, corresponding to the standard tolerance grade equal to 8, which is to be
used to define the metrological characteristic for a plain limit gauge to verify this dimensional specification.
NOTE For GO gauges, the specification limits are positioned by z and z relative to the tolerance limit of the
workpiece (see Figures 2 and 3) in order to allow a certain wear and therefore a certain time in use before the
size and form is worn outside the specification for the limit gauge.
7.2 Limit gauges for internal features of size
The positions of new state tolerance limits, and wear limits for limit gauges for internal features of size
in relation to workpiece tolerance limits are shown in Figure 2.
The NO GO gauge specification is positioned relative to the LMLS of the workpiece tolerance.
The GO gauge specification is positioned relative to the MMLS of the workpiece tolerance.
Figure 2 — MPL size position for GO and NO GO gauges for workpieces of internal feature of size
The value for H (see Figure 2) is specific for each type of limit gauge, workpiece tolerance grade and
workpiece feature size and shall be taken from Table 6.
ISO 1938-1:2015(E)
The values of z, α and y (see Figure 2) is specific for each workpiece tolerance grade and workpiece
feature size, and shall be taken from Tables 7 to 11.
When a plug gauge is used as a NO GO limit gauge (for LMLS) of a workpiece feature (LMLS ) the
W
requirement on the size, S, of the gauge element shall be in accordance with the following gauge
tolerances for new and wear limits state (see Figure 2):
H
— for the upper specification limit: USLU==SL USL −+α
U,NOGO M,NOGO W
H
— for the lower specification limit: LSLL==SL USL −−α
U,NOGO M,NOGO W
where α is equal to zero when the nominal value is up to or equal to 180 mm.
When a plug gauge is used as a GO gauge (for MMLS) of a workpiece feature (MMLS ), the requirement
w
on the size, S, of the gauge element shall be in accordance with the following gauge tolerances:
a) for the new state (see Figure 2):
H
1) for the upper specification limit: USLL=+SL z+
M, GOW
H
2) for the lower specification limit: LSLL=+SL z−
M, GOW
b) for the wear limits state (see Figure 2):
H
1) for the upper specification limit: USLL=+SL z+
U, GOW
2) for the lower specification limit: LSLL=+SL α− y
U, GOW
where
y represents an amount outside of workpiece tolerance limits taking into account a margin of wear limits
of GO gauge;
α represents a safety allowance for measurement uncertainty.
7.3 Limit gauges for external features of size
The positions of new state tolerance limits, and wear limits for limit gauges for external features of size
in relation to workpiece tolerance limits are shown in Figure 3.
The GO gauge specification is positioned relative to the MMLS of the workpiece tolerance.
The NO GO gauge specification is positioned relative to the LMLS of the workpiece tolerance.
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ISO 1938-1:2015(E)
Figure 3 — MPL size position for GO and NO GO gauges for workpieces for an external
feature of size
The value for H (see Figure 3) is specific for each
...