SIST EN ISO 1660:2017

Geometrical product specifications (GPS) - Geometrical tolerancing - Profile tolerancing (ISO 1660:2017)

This document gives the rules for geometrical specifications of integral and derived features, using the
line profile and surface profile characteristic symbols as defined in ISO 1101.

Geometrische Produktspezifikation (GPS) - Geometrische Tolerierung - Profiltolerierung (ISO 1660:2017)

Spécification géométrique des produits (GPS) - Tolérancement géométrique - Tolérancement des profils (ISO 1660:2017)

ISO 1660:2017 définit les règles pour les spécifications géométriques des éléments intégraux et dérivés, en utilisant les symboles de caractéristiques de profil de ligne et de profil de surface définis dans l'ISO 1101.

Specifikacija geometrijskih veličin izdelka (GPS) - Toleriranje geometrijskih veličin - Toleriranje profilov (ISO 1660:2017)

Ta dokument podaja pravila za geometrijske specifikacije sestavnih in izpeljanih lastnosti z značilnimi simboli linijskih in površinski profilov, kot je opredeljeno v standardu ISO 1101.

General Information

• Status: Published
• Public Enquiry End Date: 31-Jan-2014
• Publication Date: 05-Mar-2017
• ICS: 01.100.01 - Technical drawings in general
• ICS: 17.040.10 - Limits and fits
• ICS: 17.040.40 - Geometrical Product Specification (GPS)
• Technical Committee: ISEL - Mechanical elements
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 24-Feb-2017
• Due Date: 01-May-2017
• Completion Date: 06-Mar-2017
• Ref Project: EN ISO 1660:2017 - Geometrical product specifications (GPS) - Geometrical tolerancing - Profile tolerancing (ISO 1660:2017)

Relations

• Revised: SIST EN ISO 1660:2000 - Technical drawings - Dimensioning and tolerancing of profiles (ISO 1660:1987)
• Effective Date: 01-Jan-2014
• Replaces: SIST EN ISO 1660:2000 - Technical drawings - Dimensioning and tolerancing of profiles (ISO 1660:1987)
• Effective Date: 22-Feb-2017
• Replaces: SIST EN ISO 1660:2000 - Technical drawings - Dimensioning and tolerancing of profiles (ISO 1660:1987)
• Effective Date: 08-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 1660:2017
01-april-2017
1DGRPHãþD
SIST EN ISO 1660:2000

6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND*367ROHULUDQMHJHRPHWULMVNLKYHOLþLQ

7ROHULUDQMHSURILORY,62

Geometrical product specifications (GPS) - Geometrical tolerancing - Profile tolerancing

(ISO 1660:2017)

Geometrische Produktspezifikation (GPS) - Geometrische Tolerierung - Profiltolerierung

(ISO 1660:2017)
Spécification géométrique des produits (GPS) - Tolérancement géométrique -
Tolérancement des profils (ISO 1660:2017)
Ta slovenski standard je istoveten z: EN ISO 1660:2017
ICS:
01.100.01 7HKQLþQRULVDQMHQDVSORãQR Technical drawings in
general
17.040.10 Tolerance in ujemi Limits and fits
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND*36 Specification (GPS)
SIST EN ISO 1660:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 1660:2017
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SIST EN ISO 1660:2017
EN ISO 1660
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2017
EUROPÄISCHE NORM
ICS 01.100.01; 17.040.40 Supersedes EN ISO 1660:1995
English Version
Geometrical product specifications (GPS) - Geometrical
tolerancing - Profile tolerancing (ISO 1660:2017)

Spécification géométrique des produits (GPS) - Geometrische Produktspezifikation (GPS) -

Tolérancement géométrique - Tolérancement des Geometrische Tolerierung - Profiltolerierung (ISO

profils (ISO 1660:2017) 1660:2017)
This European Standard was approved by CEN on 14 December 2016.

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, Serbia, 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

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 1660:2017 E

worldwide for CEN national Members.
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SIST EN ISO 1660:2017
EN ISO 1660:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 1660:2017
EN ISO 1660:2017 (E)
European foreword

This document (EN ISO 1660:2017) 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 August 2017 and conflicting national standards shall

be withdrawn at the latest by August 2017.

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.
This document supersedes EN ISO 1660:1995.

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, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

the United Kingdom.
Endorsement notice

The text of ISO 1660:2017 has been approved by CEN as EN ISO 1660:2017 without any modification.

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SIST EN ISO 1660:2017
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SIST EN ISO 1660:2017
INTERNATIONAL ISO
STANDARD 1660
Third edition
2017-02
Geometrical product specifications
(GPS) — Geometrical tolerancing —
Profile tolerancing
Spécification géométrique des produits (GPS) — Tolérancement
géométrique — Tolérancement des profils
Reference number
ISO 1660:2017(E)
ISO 2017
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, 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 2017 – All rights reserved
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols .......................................................................................................................................................................................................................... 2

5 Rules for profile tolerancing .................................................................................................................................................................... 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Default rules for profile tolerancing ..................................................................................................................................... 4

5.2.1 Rule A: Definition of the theoretically exact feature (TEF) ......................................................... 4

5.2.2 Rule B: Type of toleranced feature ................................................................................................................... 5

5.2.3 Rule C: Definition of the tolerance zone ...................................................................................................... 5

5.3 Rules for profile tolerancing using additional specification elements ................................................... 7

5.3.1 Rule D: Toleranced feature specification elements ............................................................................ 7

5.3.2 Rule E: Unequally disposed tolerance zone .............................................................................................. 8

5.3.3 Rule F: Linear tolerance zone offset ................................................................................................................ 8

5.3.4 Rule G: Angular tolerance zone offset ............................................................................................................ 8

5.3.5 Rule H: Variable tolerance zone width .......................................................................................................... 8

5.3.6 Rule I: Filtered feature specification elements ...................................................................................... 8

5.3.7 Rule J: Association and parameter specification elements ......................................................... 9

5.3.8 Rule K: Associated toleranced feature specification elements .................. ............................... 9

5.3.9 Rule L: Non-rigid part .................................................................................................................................................. 9

Annex A (informative) Compound features ................................................................................................................................................10

Annex B (informative) Illustration of the rules ......................................................................................................................................12

Annex C (informative) Former practices .......................................................................................................................................................42

Annex D (informative) Relation to the GPS matrix model ...........................................................................................................44

Bibliography .............................................................................................................................................................................................................................45

© ISO 2017 – All rights reserved iii
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SIST EN ISO 1660:2017
ISO 1660:2017(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 World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www . i so .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product

specifications and verification.

This third edition cancels and replaces the second edition (ISO 1660:1987), which has been technically

revised with the following changes:

— the requirements for defining the theoretically exact feature (the nominal geometry) have been

made more explicit;

— the definition of what constitutes the toleranced feature has been clarified and updated to follow

the feature principle, (see ISO 8015:2011, 5.5);

— tools for defining specifications for restricted features and compound features have been added;

— tools for defining specifications using unequally disposed or offset tolerance zones have been added;

— tools for defining specifications using tolerance zone of variable width have been added.

iv © ISO 2017 – All rights reserved
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
Introduction

This document is a geometrical product specification (GPS) standard and is to be regarded as a general

GPS standard (see ISO 14638). It influences the chain links A, B and C of the chains of standards on

form, orientation and location.

The ISO GPS Masterplan 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.

For more detailed information of the relation of this document to the GPS matrix model, see Annex D.

This document provides rules for profile tolerancing.
For the presentation of lettering (proportions and dimensions), see ISO 3098-2.

All figures in this document for the 2D drawing indications have been drawn in first-angle projection

with dimensions and tolerances in millimetres. It should be understood that third-angle projection

and other units of measurement could have been used equally well without prejudice to the principles

established. For all figures giving specification examples in 3D, the dimensions and tolerances are the

same as for the similar figures shown in 2D.

The figures in this document represent either 2D drawing views or 3D axonometric views on 2D

drawings and are intended to illustrate how a specification can be fully indicated with visible

annotation. For possibilities of illustrating a specification, where elements of the specification may be

available through a query function or other interrogation of information in the 3D CAD model and rules

for attaching specifications to 3D CAD models, see ISO 16792.

The figures in this document illustrate the text and are not intended to reflect an actual application.

Consequently, the figures are not fully dimensioned and specified, showing only the relevant general

principles. Neither are the figures intended to imply a particular display requirement in terms of

whether hidden detail, tangent lines or other annotations are shown or not shown. Many figures have

lines or details removed for clarity, or added or extended to assist with the illustration of the text. See

Table 1 for the line types used in definition figures.

In order for a GPS specification to be unambiguous, the partition defining the boundary of the toleranced

feature, as well as the filtering should be well defined. Currently, the detailed rules for partitioning and

the default for filtering are not defined in GPS standards.

For a definitive presentation (proportions and dimensions) of symbols for geometrical tolerancing, see

ISO 7083 and ISO 1101:2017, Annex F.

For the purposes of this document, the terms “axis” and “median plane” are used for derived features

of perfect form, and the terms “median line” and “median surface” for derived features of imperfect

form. Furthermore, the following line types have been used in the explanatory illustrations, i.e. those

representing non-technical drawings for which the rules of ISO 128 (all parts) apply.

© ISO 2017 – All rights reserved v
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
Table 1
Line type
Feature level Feature type Details
Visible Behind plane/
surface
point
integral feature line/axis wide continuous narrow dashed
surface/plane
Nominal feature
point
narrow long dashed narrow dashed
derived feature line/axis
dotted dotted
surface/plane
surface wide freehand narrow freehand
Real feature integral feature
continuous dashed
point
integral feature line wide short dashed narrow short dashed
surface
Extracted feature
point
derived feature line wide dotted narrow dotted
surface
line
Filtered feature integral feature continuous narrow continuous narrow
surface
point narrow double-
wide doubled-dashed
integral feature straight line dashed double-
double-dotted
plane dotted
point
narrow long dashed wide dashed
Associated feature derived feature straight line (axis)
double-dotted double-dotted
plane
point
wide long dashed narrow long dashed
datum line/axis
double-short dashed double-short dashed
surface/plane
Tolerance zone lim- line
continuous narrow narrow dashed
its, tolerance planes surface
Section, illustration line
narrow long dashed narrow dashed
plane, drawing plane, surface
short dashed short dashed
aid plane
Extension, dimen- line
sion, leader and continuous narrow narrow dashed
reference lines

Contrary to other kinds of geometrical tolerancing, profile tolerancing also allows geometrical

tolerancing of non-straight lines and non-flat surfaces, in addition to simpler features, such as planes,

cylinders, etc. This makes profile tolerancing more complex than other geometrical tolerancing

with respect to the definition of the nominal geometry and the extent of the toleranced feature. This

document expands on and provides tools and rules for these two complexities.

This edition of ISO 1660 is a pilot project for writing rule-based standards for geometrical tolerancing

rather than example-based standards. In the long term, it is envisioned that the content of this document

will be integrated into a future rule-based ISO 1101.
vi © ISO 2017 – All rights reserved
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SIST EN ISO 1660:2017
ISO 1660:2017(E)

This document references other standards for rules for GPS tolerancing in general and geometrical

tolerancing in particular, rather than repeating those rules. These GPS principles and rules include, but

are not limited to:
— the feature principle (see ISO 8015:2011, 5.4);
— the independency principle (see ISO 8015:2011, 5.5);
— the rules for implicit TEDs (see ISO 5458:1998, 4.3);

— the width of the tolerance zone applies normal to the toleranced feature (See ISO 1101:2017,

Clause 7);

— the rules for identifying the toleranced features (see ISO 1101:2017, Clause 6 and 9.1);

— form specifications, i.e. specifications without reference to a datum, a datum system or a pattern,

constrain neither orientation nor location (see ISO 1101:2017, 4.8);
— the tolerance zone can be constrained by reference to datums (see ISO 5459).
© ISO 2017 – All rights reserved vii
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SIST EN ISO 1660:2017
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SIST EN ISO 1660:2017
INTERNATIONAL STANDARD ISO 1660:2017(E)
Geometrical product specifications (GPS) — Geometrical
tolerancing — Profile tolerancing

IMPORTANT — The illustrations included in this document are intended to illustrate the text

and/or to provide examples of the related technical drawing specification; these illustrations are

not fully dimensioned and toleranced, showing only the relevant general principles. In particular,

the illustrations do not contain filter specifications. As a consequence, the illustrations are not

a representation of a complete workpiece and are not of a quality that is required for use in

industry (in terms of full conformity with the standards prepared by ISO/TC 10 and ISO/TC 213),

and as such are not suitable for projection for teaching purposes.
1 Scope

This document gives the rules for geometrical specifications of integral and derived features, using the

line profile and surface profile characteristic symbols as defined in ISO 1101.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 1101:2017, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,

orientation, location and run-out

ISO 5459:2011, Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and

datum systems

ISO 8015:2011, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules

ISO 16792, Technical product documentation — Digital product definition data practices

ISO 17450-1, Geometrical product specifications (GPS) — General concepts — Part 1: Model for geometrical

specification and verification

ISO 17450-3, Geometrical product specifications (GPS) — General concepts — Part 3: Toleranced features

ISO 22432, Geometrical product specifications (GPS) — Features utilized in specification and verification

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1101, ISO 5459, ISO 8015,

ISO 17450-1, ISO 17450-3, ISO 22432 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
profile tolerancing

geometrical tolerancing using the line profile symbol or the surface profile symbol

© ISO 2017 – All rights reserved 1
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
3.2
line profile
property of a line
3.3
surface profile
property of a surface
3.4
non-redundant degree of freedom
degree of freedom for which the tolerance zone is not invariant
4 Symbols
See Table 2.
Table 2 — Symbols for geometrical characteristics
Line profile symbol
Surface profile symbol

These symbols shall be used in the characteristic section of the tolerance indicator, see ISO 1101:2017, 8.2.

The nominal features, for which each symbol can be used, are given in Table 3.
Table 3 — Valid geometrical characteristic symbol and nominal toleranced feature
combinations
Toleranced feature
Integral straight line X
Derived straight line X
Integral non-straight line X
Derived non-straight line X
Integral flat surface X
Derived flat surface X
Integral non-flat surface X
Derived non-flat surface X

For straight lines and planes, there are other characteristic symbols that directly provide the

information about the shape of the toleranced feature, e.g. flatness for planes and straightness for

straight lines. The profile characteristic symbols may be used for straight lines and planes. However, in

this case, to determine the nominal shape of the toleranced feature, it is necessary to verify that there is

no indication that the feature is nominally non-flat or non-straight on the drawing or in the CAD model,

as applicable.

NOTE A nominally planar surface and a nominally curved surface with a large radius may both appear as

a straight line on the drawing and the profile characteristic symbols can be used for both types of surfaces.

However, for the curved surface there will be an indication on the drawing or explicit or implicit TEDs in the

CAD model, that the surface is not flat. For the planar surface, there will be no such indication on a drawing. On a

drawing, it is this indication or absence of indication that is used to determine the nominal shape of the feature in

this case. In a CAD model, the model data are used to determine the nominal shape of the feature.

Additional symbols used in this document are given in Table 4 along with a reference to where they are

defined.
2 © ISO 2017 – All rights reserved
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
Table 4 — Additional symbols used in this document
Description Symbol Reference
Combined zone ISO 1101:2017, 8.2.2.1.2
Separate zones ISO 1101:2017, 8.2.2.1.2
Unspecified linear tolerance zone offset ISO 1101:2017, 8.2.2.1.4.1
Specified tolerance zone offset ISO 1101:2017, 8.2.2.1.3
United feature ISO 1101:2017, 3.9
Between ISO 1101:2017, 9.1.4
Unspecified angular tolerance zone offset ISO 1101:2017, 8.2.2.1.4.2
All around ISO 1101:2017, 9.1.2
All over ISO 1101:2017, 9.1.2
Collection plane indicator ISO 1101:2017, 16
Intersection plane indicator ISO 1101:2017, 13
Direction feature indicator ISO 1101:2017, 15
Orientation constraint only ISO 5459:2011, 7.4.2.8
5 Rules for profile tolerancing
5.1 General

For the basic rules for geometrical tolerancing, of which profile tolerancing is a part, see ISO 1101.

When a drawing shall be used in conjunction with a CAD model, an unambiguous reference to the CAD

model shall be made on the drawing and the CAD model shall comply with ISO 16792.

According to the feature principle (see ISO 8015:2011, 5.4), by default a profile specification applies

to one complete single feature as defined in ISO 22432. It is the designer’s responsibility to select the

features or parts of features to which a specification applies and either indicate that on a 2D drawing

using appropriate symbology or define it in the CAD model.

According to the independency principle (see ISO 8015:2011, 5.5), by default a profile specification that

applies to more than one single feature as defined in ISO 22432, applies to those features independently.

If it is desired that the profile specification applies to the features as if they were one, or with some

constraint amongst the tolerance zones for the single features, it is the designer’s responsibility to

either indicate this on a 2D drawing using appropriate symbology or define it in the CAD model.

The “all over” indication and the “all around” indication shall always be combined with UF, CZ or SZ,

when used for geometrical tolerancing, to make it explicit whether the specification applies to a united

feature, defines a combined zone or defines a set of separate zones, except when all the non-redundant

degrees of freedom for all the tolerance zones are locked by reference to datums.

NOTE 1 The meaning of CZ and SZ is identical when the specification defines a set of tolerance zones for which

all non-redundant degrees of freedom are locked by reference to datums.

NOTE 2 In previous revisions of this document, “all around” was used without any other indication. That

made it ambiguous whether the specification applied to the features independently or the specification defined a

combined zone. The requirement to always use UF, CZ or SZ is a failsafe indication.

© ISO 2017 – All rights reserved 3
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SIST EN ISO 1660:2017
ISO 1660:2017(E)
5.2 Default rules for profile tolerancing
5.2.1 Rule A: Definition of the theoretically exact feature (TEF)

The theoretically exact feature (TEF) of the toleranced feature shall be defined with theoretically exact

dimensions (TEDs) or be embedded in the CAD model. For a feature of size, the nominal shape of the

TEF shall be defined, but the nominal size of the TEF may be undefined, see Figure 4 b).

These TEDs may include:
— explicit TEDs;
— implicit TEDs;
— tables of values and interpolation algorithms;
— mathematical functions including splines and other formulae;
— reference to CAD model queries.

A TEF that appears to be a nominally straight line or a nominal plane on the drawing with no explicit

indication to the contrary, shall be considered a nominally straight line or a nominal plane, respectively,

defined by implicit TEDs.

The shape of a TEF that is nominally a circle, a cylinder, a sphere or a cone is implicitly defined.

The shape of a TEF that is nominally a torus is defined when the directrix size is defined by an

explicit TED.

The size of a feature of size is undefined, and shall therefore be considered variable, unless it is defined

by an explicit TED, see Figures 1 and 4. The size of the generatrix of a torus is undefined, unless it is

defined by an explicit TED. See also rules F and G.

NOTE The diameter of the median surface of the tolerance zone is fixed at the nominal size.

Figure 1 — Surface profile specification for a sphere of defined nominal size, giv

...