ISO2768-1
BRITISH STANDARD BS EN
22768-2:1993
ISO 2768-2:
1989
General tolerances —
Part 2: Geometrical tolerances for features without individual tolerance indications
The European Standard EN 22768-2:1993 has the status of a
British Standard
UDC 621.713.14:744.4
BS EN 22768-2:1993
Cooperating organizations
The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries:
Austria Oesterreichisches Normungsinstitut Belgium Institut belge de normalisation Denmark Dansk Standardiseringsraad
Finland Suomen Standardisoimisliito, r.y.
France Association française de normalisation
Germany Deutsches Institut für Normung e.V.
Greece Hellenic Organization for Standardization
Iceland Technological Institute of Iceland
Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund
Portugal Instituto Portuguès da Qualidade
Spain Asociación Española de Normalización y Certificación
Sweden Standardiseringskommissionen i Sverige
Switzerland Association suisse de normalisation
United Kingdom British Standards Institution
This British Standard, having
been prepared under the direction of the Machine, Engineers and Hand Tools Standards Policy Committee, was published under the authority of the Standards Board and comes
into effect on
15 July 1993
© BSI 03-1999
The following BSI references relate to the work on this standard:
Committee reference MTE/24
Draft for comment 87/78364 DC
ISBN 0 580 21934 8
Amendments issued since publication
BS EN 22768-2:1993
Contents
Page Cooperating organizations Inside front cover National foreword ii
Foreword 2
Introduction 3
1 Scope 3
2 General 3
3 Normative references 3
4 Definitions 3
5 General geometrical tolerances 3
6 Indications on drawings 5
7 Rejection 5
Annex A (informative) Concepts behind general tolerancing of
geometrical characteristics 6
Annex B (informative) Further information 7
Annex ZA (normative) Normative references to international publications
with their relevant European publications 10
Figure B.1 — Principle of independency: maximum permissible
deviations on the same feature 7
Figure B.2 — Examples of general tolerances on circularity 8
Figure B.3 — Parallelism deviation equal to the numerical value of the
size tolerance 8
Figure B.4 — Parallelism deviation equal to the numerical value of the straightness tolerance 8
Figure B.5 — Examples of general tolerances on symmetry 8
Figure B.6 — Example of general tolerances on a drawing 9
Table 1 — General tolerances on straightness and flatness 4
Table 2 — General tolerances on perpendicularity 4
Table 3 — General tolerances on symmetry 4
Table 4 — General tolerances on circular run-out 5
National annex NA (informative) Committees responsible Inside back cover
© BSI 03-1999 i
BS EN 22768-2:1993
National foreword
This British Standard has been prepared under the direction of the Machine, Engineers and Hand Tools Standards Policy Committee and is the English language version of EN 22768-2:1993 General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications, published by the European Committee for Standardization (CEN). It is identical
with ISO 2768-2:1989 published by the International Organization for
Standardization (ISO).
A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity from legal obligations.
Summary of pages
This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 10, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.
ii © BSI 03-1999
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 22768-2
April 1993
UDC 621.713.14:744.4
Descriptors: Machine components, geometrical tolerances, machining tolerances, dimensional deviations, specifications
English version
General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications
(ISO 2768-2:1989)
Tolérances générales — Partie 2: Tolérances
géométriques pour éléments non affectés de tolérances individuelles
(ISO 2768-2:1989)
Allgemeintoleranzen — Teil 2: Toleranzen für
Form und Lage ohne einzelne
Toleranzeintragung
(ISO 2768-2:1989)
This European Standard was approved by CEN on 1993-04-15. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CEN
European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung
Central Secretariat: rue de Stassart 36, B-1050 Brussels
© 1993 Copyright reserved to CEN members
Ref. No. EN 22768-2:1993 E
EN 22768-2:1993
Introduction
All features on component parts always have a size and a geometrical shape. For the deviation of size and for the deviations of the geometrical characteristics (form, orientation and location) the function of the part requires limitations which,
when exceeded, impair this function.
The tolerancing on the drawing should be complete to ensure that the elements of size and geometry of all features are controlled, i.e. nothing shall be implied or left to judgement in the workshop or in the inspection department.
The use of general tolerances for size and geometry simplifies the task of ensuring that this prerequisite is met.
1 Scope
This part of ISO 2768 is intended to simplify drawing indications and specifies general geometrical tolerances to control those features on the drawing which have no respective individual indication. It specifies general geometrical tolerances in three tolerance classes.
This part of ISO 2768 mainly applies to features which are produced by removal of material. Its application to features manufactured by other processes is possible; however, special examination is required to ascertain whether the customary workshop accuracy lies within the general geometrical tolerances specified in this part
of ISO 2768.
2 General
When selecting the tolerance class, the respective customary workshop accuracy has to be taken into consideration. If smaller geometrical tolerances are required or larger geometrical tolerances are permissible and more economical for any individual feature, such tolerances should be indicated directly in accordance with ISO 1101 (see clause A.2).
General geometrical tolerances in accordance with this part of ISO 2768 apply when drawings or associated specifications refer to this part of
ISO 2768 in accordance with clause 6. They apply to features which do not have respective individual
geometrical tolerance indications.
General geometrical tolerances apply to all geometrical tolerance characteristics, excluding cylindricity, profile of any line, profile of any
surface, angularity, coaxiality, positional tolerances and total run-out.
In any event, general geometrical tolerances in
accordance with this part of ISO 2768 should be used when the fundamental tolerancing principle in accordance with ISO 8015 is used and indicated on the drawing (see clause B.1).
3 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 2768. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 2768 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 1101:1983, Technical drawings — Geometrical tolerancing — Tolerancing of form, orientation, location and run-out — Generalities, definitions, symbols, indications on drawings.
ISO 2768-1:1989, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications.
ISO 5459:1981, Technical drawings — Geometrical tolerancing — Datums and datum-systems for geometrical tolerances.
ISO 8015:1985, Technical drawings — Fundamental tolerancing principle.
4 Definitions
For the purposes of this part of ISO 2768, the definitions for geometrical tolerances given in ISO 1101 and ISO 5459 apply.
5 General geometrical tolerances
(see also clause B.1)
5.1 Tolerances for single features
5.1.1 Straightness and flatness
The general tolerances on straightness and flatness are given in Table 1. When a tolerance is selected from Table 1, it shall be based, in the case of straightness, on the length of the corresponding line and, in the case of flatness, on the longer lateral length of the surface, or the diameter of the circular surface.
© BSI 03-1999 3
EN 22768-2:1993
Table 1 — General tolerances on straightness
and flatness
Values in millimetres
Table 2 — General tolerances on
perpendicularity
Values in millimetres
Tolerance class Perpendicularity tolerances for ranges of nominal lengths of the shorter side
up to 100 over 100
up to 300 over 300
up to 1 000 over 1 000
up to 3 000
H 0,2 0,3 0,4 0,5
K 0,4 0,6 0,8 1
L 0,6 1 1,5 2
5.1.2 Circularity
The general tolerance on circularity is equal to the numerical value of the diameter tolerance, but in no case shall it be greater than the respective tolerance value for circular radial run-out given in Table 4
(see examples in clause B.2).
5.1.3 Cylindricity
General tolerances on cylindricity are not specified.
NOTE 1 The cylindricity deviation comprises three components: circularity deviation, straightness deviation and parallelism deviation of opposite generator lines. Each of these components is controlled by its individually indicated or its general tolerance.
NOTE 2 If, for functional reasons, the cylindricity deviation has to be smaller than the combined effect (see clause B.3) of the general tolerances on circularity, straightness and parallelism,
an individual cylindricity tolerance in accordance with ISO 1101
should be indicated for the feature concerned.
Sometimes, e.g. in the case of a fit, the indication of the envelope requiremen is appropriate.
5.2 Tolerances for related features
5.2.1 General
The tolerances specified in 5.2.2 to 5.2.6 apply to all features which are in relation to one another and which have no respective individual indication.
5.2.2 Parallelism
The general tolerance on parallelism is equal to the numerical value of the size tolerance or the flatness/straightness tolerance, whichever is the greater. The longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum
(see clause B.4).
5.2.3 Perpendicularity
The general tolerances on perpendicularity are
given in Table 2. The longer of the two sides forming the right angle shall be taken as the datum; if the sides are of equal nominal length, either may be taken as the datum.
5.2.4 Symmetry
The general tolerances on symmetry are given
in Table 3. The longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum.
NOTE The general tolerances on symmetry apply where
— at least one of the two features has a median plane, or
— the axes of the two features are perpendicular to each other.
See examples in clause B.5.
Table 3 — General tolerances on symmetry
Values in millimetres
Tolerance class Symmetry tolerances for ranges of nominal lengths
up to 100 over 100
up to 300 over 300
up to 1 000 over 1 000
up to 3 000
H 0,5
K 0,6 0,8 1
L 0,6 1 1,5 2
5.2.5 Coaxiality
General tolerances on coaxiality are not specified.
NOTE The deviation in coaxiality may, in an extreme case, be as great as the tolerance value for circular radial run-out given
in Table 4, since the deviation in radial run-out comprises the deviation in coaxiality and the deviation in circularity.
5.2.6 Circular run-out
The general tolerances on circular run-out
(radial, axial and any surface of revolution) are given in Table 4.
For general tolerances on circular run-out, the bearing surfaces shall be taken as the datum if they are designated as such. Otherwise, for circular radial run-out, the longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum.
4 © BSI 03-1999
EN 22768-2:1993
Table 4 — General tolerances on circular
run-out
Values in millimetres
Tolerance class Circular run-out tolerances
H 0,1
K 0,2
L 0,5
6 Indications on drawings
6.1 If general tolerances in accordance with this
part of ISO 2768 shall apply in conjunction with the general tolerances in accordance with ISO 2768-1, the following information shall be indicated in or near the title block:
a) “ISO 2768”;
b) the tolerance class in accordance with ISO 2768-1;
c) the tolerance class in accordance with this part of ISO 2768.
EXAMPLE
ISO 2768-mk
In this case the general tolerances for angular dimensions in accordance with ISO 2768-1 do not apply to right angles (90°), which are implied but not indicated, because this part of ISO 2768 specifies general tolerances on perpendicularity.
6.2 If the general dimensional tolerances (tolerance
class m) shall not apply, the respective letter shall be omitted from the designation to be indicated on the drawing:
EXAMPLE
ISO 2768-K
In cases where the envelope requirement also applies to all single features of size1), the designation “E” shall be added to the general designation specified in 6.1:
EXAMPLE
ISO 2768-mK-E
NOTE The envelope requiremen cannot apply to features with individually indicated straightness tolerances which are greater than their size tolerances, e.g. stock material.
7 Rejection
Unless otherwise stated, workpieces exceeding the general geometrical tolerance shall not lead to automatic rejection provided that the ability of the workplace to function is not impaired
(see clause A.4).
1) For the purposes of this part of ISO 2768, a single feature of size comprises a cylindrical surface or two parallel plane surfaces.
© BSI 03-1999 5
EN 22768-2:1993
Annex A (informative)
Concepts behind general tolerancing of geometrical characteristics
A.1 General tolerances should be indicated on the drawing by reference to this part of ISO 2768 in accordance with clause 6.
The values of general tolerances correspond to grades of customary workshop accuracy, the appropriate tolerance class being selected and indicated on the drawing.
A.2 Above a certain tolerance value, which corresponds to the customary workshop accuracy, there is usually no gain in manufacturing economy by enlarging the tolerance. In any event, workshop machinery and the usual workmanship normally do not manufacture features with greater deviations. For example, a feature of 25 mm ± 0,1 mm diameter by 80 mm long manufactured in a workshop with a customary accuracy equal to or finer than
ISO 2768-mH contains the geometrical deviations well within 0,1 mm for circularity, 0,1 mm for straightness of surface elements, and 0,1 mm for circular radial run-out (the values given have been taken from this part of ISO 2768). Specifying tolerances would be of no benefit in this particular workshop.
However, if, for functional reasons, a feature requires a smaller tolerance value than the “general tolerances”, then that feature should have the smaller tolerance indicated individually adjacent to the particular feature. This type of tolerance falls out-side the scope of general tolerances.
In cases where the function of a feature allows a geometrical tolerance equal to or larger than the general tolerance values, this should not be individually indicated, but should be stated on the drawing as described in clause 6. This type of tolerance allows full use of the concept of general geometrical tolerancing.
There will be “exceptions to the rule” where the function allows a larger tolerance than the general tolerances, and the larger tolerance will provide a gain in manufacturing economy. In these special cases, the larger geometrical tolerance should be indicated individually adjacent to the particular feature, e.g. the circularity tolerance of a large and thin ring.
A.3 Using general geometrical tolerances leads to the following advantages:
a) drawings are easier to read and thus communication is made more effective to the user of the drawing;
b) the design draughtsman saves time by
avoiding detailed tolerance calculations as it is sufficient only to know that the function allows a tolerance greater than or equal to the general tolerance;
c) the drawing readily indicates which features can be produced by normal process capability, which also assists quality engineering by reducing inspection levels;
d) those features remaining, which have individually indicated geometrical tolerances, will, for the most part, be those controlling features for which the function requires relatively small tolerances and which therefore
may cause special effort in the production — this will be helpful for production planning and will assist quality control services in their analysis of inspection requirements;
e) purchase and subcontract supply engineers can negotiate orders more readily since the
“customary workshop accuracy” is known before the contract is placed; this also avoids arguments on delivery between the buyer and the supplier,
since in this respect the drawing is complete.
These advantages are fully obtained only when there is sufficient reliability that the general tolerances will not be exceeded, i.e. when the customary workshop accuracy of the particular workshop is equal to or finer than the general tolerances indicated in the drawing.
The workshop should, therefore,
— find out by measurements what its customary workshop accuracy is;
— accept only those drawings having general tolerances equal to or greater than its customary workshop accuracy;
— check by sampling that its customary workshop accuracy does not deteriorate.
Relying on undefined “good workmanship” with all its uncertainties and misunderstandings is no longer necessary with the concept of general geometrical tolerances. The general geometrical tolerances define the required accuracy of “good workmanship”.
A.4 The tolerance the function allows is often greater than the general tolerance. The function of the part is, therefore, not always impaired when the general tolerance is (occasionally) exceeded at any feature of the workpiece. Exceeding the general tolerance should lead to a rejection of the workpiece only if the function is impaired.
6 © BSI 03-1999
EN 22768-2:1993
Annex B (informative)
Further information
B.1 General geometrical tolerances
(see clause 5)
According to the principle of independency
(see ISO 8015), general geometrical tolerances apply independently of the actual local size of the workpiece features. Accordingly, the general geometrical tolerances may be used even if the
features are everywhere at their maximum material
size (see Figure B.1).
If the envelope requiremen is individually indicated adjacent to the feature or generally to all features of size as described in clause 6, this requirement should also be complied with.
B.2 Circularity (see 5.1.2) — Examples
EXAMPLE 1 (see Figure B.2)
The permissible deviation of the diameter is indicated directly on the drawing; the general tolerance on circularity is equal to the numerical value of the diameter tolerance.
EXAMPLE 2 (see Figure B.2)
The general tolerances in accordance with the
indication ISO 2768-mK apply. The permissible deviations for the diameter of 25 mm are ± 0,2 mm. These deviations lead to the numerical value
of 0,4 mm which is greater than the value of 0,2 mm given in Table 4; the value of 0,2 mm, therefore,
applies for the circularity tolerance.
B.3 Cylindricity (see note 2 in 5.1.3)
The combined effect of the general tolerances of circularity, straightness and parallelism is, for geometrical reasons, smaller than the sum of the three tolerances since there is also a certain limitation by the size tolerance. However, for the sake of simplicity, in order to decide whether the envelope requirement or an individual cylindricity tolerance is to be indicated, the sum of the three tolerances can be taken into account.
B.4 Parallelism (see 5.2.2)
Depending on the shapes of the deviations of the features, the parallelism deviation is limited by the numerical value of the size tolerance
(see Figure B.3) or by the numerical value of the straightness or flatness tolerance (see B.4).
Figure B.1 — Principal of independency; maximum permissible deviations on the same
feature
© BSI 03-1999 7
EN 22768-2:1993
Example Indication on the drawing
Values in millimetres
Circularity tolerance zone
B.5 Symmetry (see 5.2.4) — Examples
1
2
Figure B.2 — Examples of general tolerances on circularity
Figure B.3 — Parallelism deviation equal to the numerical value of the size tolerance
Figure B.4 — Parallelism deviation equal to the numerical value of the straightness tolerance
Figure B.5 — Example of general tolerances
on symmetry (datums specified in accordance with 5.2.4)
8 © BSI 03-1999
EN 22768-2:1993
B.6 Example of a drawing
NOTE 1 The tolerances shown in chain thin double-dashed lines (boxes and circles) are general tolerances. These tolerance values would be automatically achieved by machining in a workshop with a customary accuracy equal to or finer than ISO 2768-mH and would not normally require to be inspected.
NOTE 2 As some tolerances also limit the deviations of other characteristics of the same feature, e.g. the perpendicularity tolerance also limits the straightness deviations, not all general tolerance are shown in the interpretation above.
Figure B.6 — Example of general tolerances on a drawing
© BSI 03-1999 9
EN 22768-2:1993
Annex ZA (informative)
Normative references to international publications with their relevant
European publications
This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply
to this European Standard only when incorporated in it by amendment or revision. For undated references
the latest edition of the publication referred to applies (including amendments).
Publication Title EN/HD
ISO 1101 Technical drawings — Geometrical tolerancing — Tolerances
of form, orientation, location and run-out — Generalities, definitions, symbols, indications on drawings
ISO 2768-1 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
ISO 5459 Technical drawings — Geometrical tolerancing — Datums and datum-systems for geometrical tolerances
ISO 8015 Technical drawings — Fundamental tolerancing principle
EN 22768-1
10 © BSI 03-1999
BS EN 22768-2:1993
National annex NA (informative)
Committees responsible
The United Kingdom participation in the preparation of this European Standard was entrusted by the Machine, Engineers and Hand Tools Standards Policy Committee (MTE/-) to Technical Committee MTE/24, upon which the following bodies were represented:
British Cast Iron Research Association
British Electrical and Allied Manufacturers’ Association
British Foundry Association
Federation of British Engineers Tool Manufacturers
Railway Industry Association of Great Britain Society of British Aerospace Companies Ltd. Society of Motor Manufacturers and Traders Ltd. Zinc Development Association
Coopted members
© BSI 03-1999
BSI
389 Chiswick High Road
London
W4 4AL
|
|
|
|
|
|
| BSI ￐ British Standards Institution
|
|
|
|
|
|
| BSI is the independent national body responsible for preparing British Standards. It
|
| presents the UK view on standards in Europe and at the international level. It is
| incorporated by Royal Charter.
|
| Revisions
|
| British Standards are updated by amendment or revision. Users of British Standards
| should make sure that they possess the latest amendments or editions.
|
| It is the constant aim of BSI to improve the quality of our products and services. We
|
| would be grateful if anyone finding an inaccuracy or ambiguity while using this
| British Standard would inform the Secretary of the technical committee responsible,
| the identity of which can be found on the inside front cover. Tel: 020 8996 9000.
| Fax: 020 8996 7400.
|
| BSI offers members an individual updating service called PLUS which ensures that
| subscribers automatically receive the latest editions of standards.
|
|
| Buying standards
|
| Orders for all BSI, international and foreign standards publications should be
| addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001.
|
| In response to orders for international standards, it is BSI policy to supply the BSI
| implementation of those that have been published as British Standards, unless
| otherwise requested.
|
|
| Information on standards
|
| BSI provides a wide range of information on national, European and international
| standards through its Library and its Technical Help to Exporters Service. Various
| BSI electronic information services are also available which give details on all its
| products and services. Contact the Information Centre. Tel: 020 8996 7111.
| Fax: 020 8996 7048.
|
|
| Subscribing members of BSI are kept up to date with standards developments and
| receive substantial discounts on the purchase price of standards. For details of
| these and other benefits contact Membership Administration. Tel: 020 8996 7002.
| Fax: 020 8996 7001.
|
| Copyright
|
| Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of
|
| the publications of the international standardization bodies. Except as permitted
| under the Copyright, Designs and Patents Act 1988 no extract may be reproduced,
| stored in a retrieval system or transmitted in any form or by any means ﾱ electronic,
| photocopying, recording or otherwise ﾱ without prior written permission from BSI.
|
| This does not preclude the free use, in the course of implementing the standard, of
| necessary details such as symbols, and size, type or grade designations. If these
|
| details are to be used for any other purpose than implementation then the prior
| written permission of BSI must be obtained.
|
| If permission is granted, the terms may include royalty payments or a licensing
| agreement. Details and advice can be obtained from the Copyright Manager.
| Tel: 020 8996 7070.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
22768-2:1993
ISO 2768-2:
1989
General tolerances —
Part 2: Geometrical tolerances for features without individual tolerance indications
The European Standard EN 22768-2:1993 has the status of a
British Standard
UDC 621.713.14:744.4
BS EN 22768-2:1993
Cooperating organizations
The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries:
Austria Oesterreichisches Normungsinstitut Belgium Institut belge de normalisation Denmark Dansk Standardiseringsraad
Finland Suomen Standardisoimisliito, r.y.
France Association française de normalisation
Germany Deutsches Institut für Normung e.V.
Greece Hellenic Organization for Standardization
Iceland Technological Institute of Iceland
Ireland National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund
Portugal Instituto Portuguès da Qualidade
Spain Asociación Española de Normalización y Certificación
Sweden Standardiseringskommissionen i Sverige
Switzerland Association suisse de normalisation
United Kingdom British Standards Institution
This British Standard, having
been prepared under the direction of the Machine, Engineers and Hand Tools Standards Policy Committee, was published under the authority of the Standards Board and comes
into effect on
15 July 1993
© BSI 03-1999
The following BSI references relate to the work on this standard:
Committee reference MTE/24
Draft for comment 87/78364 DC
ISBN 0 580 21934 8
Amendments issued since publication
BS EN 22768-2:1993
Contents
Page Cooperating organizations Inside front cover National foreword ii
Foreword 2
Introduction 3
1 Scope 3
2 General 3
3 Normative references 3
4 Definitions 3
5 General geometrical tolerances 3
6 Indications on drawings 5
7 Rejection 5
Annex A (informative) Concepts behind general tolerancing of
geometrical characteristics 6
Annex B (informative) Further information 7
Annex ZA (normative) Normative references to international publications
with their relevant European publications 10
Figure B.1 — Principle of independency: maximum permissible
deviations on the same feature 7
Figure B.2 — Examples of general tolerances on circularity 8
Figure B.3 — Parallelism deviation equal to the numerical value of the
size tolerance 8
Figure B.4 — Parallelism deviation equal to the numerical value of the straightness tolerance 8
Figure B.5 — Examples of general tolerances on symmetry 8
Figure B.6 — Example of general tolerances on a drawing 9
Table 1 — General tolerances on straightness and flatness 4
Table 2 — General tolerances on perpendicularity 4
Table 3 — General tolerances on symmetry 4
Table 4 — General tolerances on circular run-out 5
National annex NA (informative) Committees responsible Inside back cover
© BSI 03-1999 i
BS EN 22768-2:1993
National foreword
This British Standard has been prepared under the direction of the Machine, Engineers and Hand Tools Standards Policy Committee and is the English language version of EN 22768-2:1993 General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications, published by the European Committee for Standardization (CEN). It is identical
with ISO 2768-2:1989 published by the International Organization for
Standardization (ISO).
A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity from legal obligations.
Summary of pages
This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages 2 to 10, an inside back cover and a back cover.
This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.
ii © BSI 03-1999
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 22768-2
April 1993
UDC 621.713.14:744.4
Descriptors: Machine components, geometrical tolerances, machining tolerances, dimensional deviations, specifications
English version
General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications
(ISO 2768-2:1989)
Tolérances générales — Partie 2: Tolérances
géométriques pour éléments non affectés de tolérances individuelles
(ISO 2768-2:1989)
Allgemeintoleranzen — Teil 2: Toleranzen für
Form und Lage ohne einzelne
Toleranzeintragung
(ISO 2768-2:1989)
This European Standard was approved by CEN on 1993-04-15. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CEN
European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung
Central Secretariat: rue de Stassart 36, B-1050 Brussels
© 1993 Copyright reserved to CEN members
Ref. No. EN 22768-2:1993 E
EN 22768-2:1993
Introduction
All features on component parts always have a size and a geometrical shape. For the deviation of size and for the deviations of the geometrical characteristics (form, orientation and location) the function of the part requires limitations which,
when exceeded, impair this function.
The tolerancing on the drawing should be complete to ensure that the elements of size and geometry of all features are controlled, i.e. nothing shall be implied or left to judgement in the workshop or in the inspection department.
The use of general tolerances for size and geometry simplifies the task of ensuring that this prerequisite is met.
1 Scope
This part of ISO 2768 is intended to simplify drawing indications and specifies general geometrical tolerances to control those features on the drawing which have no respective individual indication. It specifies general geometrical tolerances in three tolerance classes.
This part of ISO 2768 mainly applies to features which are produced by removal of material. Its application to features manufactured by other processes is possible; however, special examination is required to ascertain whether the customary workshop accuracy lies within the general geometrical tolerances specified in this part
of ISO 2768.
2 General
When selecting the tolerance class, the respective customary workshop accuracy has to be taken into consideration. If smaller geometrical tolerances are required or larger geometrical tolerances are permissible and more economical for any individual feature, such tolerances should be indicated directly in accordance with ISO 1101 (see clause A.2).
General geometrical tolerances in accordance with this part of ISO 2768 apply when drawings or associated specifications refer to this part of
ISO 2768 in accordance with clause 6. They apply to features which do not have respective individual
geometrical tolerance indications.
General geometrical tolerances apply to all geometrical tolerance characteristics, excluding cylindricity, profile of any line, profile of any
surface, angularity, coaxiality, positional tolerances and total run-out.
In any event, general geometrical tolerances in
accordance with this part of ISO 2768 should be used when the fundamental tolerancing principle in accordance with ISO 8015 is used and indicated on the drawing (see clause B.1).
3 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO 2768. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 2768 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 1101:1983, Technical drawings — Geometrical tolerancing — Tolerancing of form, orientation, location and run-out — Generalities, definitions, symbols, indications on drawings.
ISO 2768-1:1989, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications.
ISO 5459:1981, Technical drawings — Geometrical tolerancing — Datums and datum-systems for geometrical tolerances.
ISO 8015:1985, Technical drawings — Fundamental tolerancing principle.
4 Definitions
For the purposes of this part of ISO 2768, the definitions for geometrical tolerances given in ISO 1101 and ISO 5459 apply.
5 General geometrical tolerances
(see also clause B.1)
5.1 Tolerances for single features
5.1.1 Straightness and flatness
The general tolerances on straightness and flatness are given in Table 1. When a tolerance is selected from Table 1, it shall be based, in the case of straightness, on the length of the corresponding line and, in the case of flatness, on the longer lateral length of the surface, or the diameter of the circular surface.
© BSI 03-1999 3
EN 22768-2:1993
Table 1 — General tolerances on straightness
and flatness
Values in millimetres
Table 2 — General tolerances on
perpendicularity
Values in millimetres
Tolerance class Perpendicularity tolerances for ranges of nominal lengths of the shorter side
up to 100 over 100
up to 300 over 300
up to 1 000 over 1 000
up to 3 000
H 0,2 0,3 0,4 0,5
K 0,4 0,6 0,8 1
L 0,6 1 1,5 2
5.1.2 Circularity
The general tolerance on circularity is equal to the numerical value of the diameter tolerance, but in no case shall it be greater than the respective tolerance value for circular radial run-out given in Table 4
(see examples in clause B.2).
5.1.3 Cylindricity
General tolerances on cylindricity are not specified.
NOTE 1 The cylindricity deviation comprises three components: circularity deviation, straightness deviation and parallelism deviation of opposite generator lines. Each of these components is controlled by its individually indicated or its general tolerance.
NOTE 2 If, for functional reasons, the cylindricity deviation has to be smaller than the combined effect (see clause B.3) of the general tolerances on circularity, straightness and parallelism,
an individual cylindricity tolerance in accordance with ISO 1101
should be indicated for the feature concerned.
Sometimes, e.g. in the case of a fit, the indication of the envelope requiremen is appropriate.
5.2 Tolerances for related features
5.2.1 General
The tolerances specified in 5.2.2 to 5.2.6 apply to all features which are in relation to one another and which have no respective individual indication.
5.2.2 Parallelism
The general tolerance on parallelism is equal to the numerical value of the size tolerance or the flatness/straightness tolerance, whichever is the greater. The longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum
(see clause B.4).
5.2.3 Perpendicularity
The general tolerances on perpendicularity are
given in Table 2. The longer of the two sides forming the right angle shall be taken as the datum; if the sides are of equal nominal length, either may be taken as the datum.
5.2.4 Symmetry
The general tolerances on symmetry are given
in Table 3. The longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum.
NOTE The general tolerances on symmetry apply where
— at least one of the two features has a median plane, or
— the axes of the two features are perpendicular to each other.
See examples in clause B.5.
Table 3 — General tolerances on symmetry
Values in millimetres
Tolerance class Symmetry tolerances for ranges of nominal lengths
up to 100 over 100
up to 300 over 300
up to 1 000 over 1 000
up to 3 000
H 0,5
K 0,6 0,8 1
L 0,6 1 1,5 2
5.2.5 Coaxiality
General tolerances on coaxiality are not specified.
NOTE The deviation in coaxiality may, in an extreme case, be as great as the tolerance value for circular radial run-out given
in Table 4, since the deviation in radial run-out comprises the deviation in coaxiality and the deviation in circularity.
5.2.6 Circular run-out
The general tolerances on circular run-out
(radial, axial and any surface of revolution) are given in Table 4.
For general tolerances on circular run-out, the bearing surfaces shall be taken as the datum if they are designated as such. Otherwise, for circular radial run-out, the longer of the two features shall be taken as the datum; if the features are of equal nominal length, either may be taken as the datum.
4 © BSI 03-1999
EN 22768-2:1993
Table 4 — General tolerances on circular
run-out
Values in millimetres
Tolerance class Circular run-out tolerances
H 0,1
K 0,2
L 0,5
6 Indications on drawings
6.1 If general tolerances in accordance with this
part of ISO 2768 shall apply in conjunction with the general tolerances in accordance with ISO 2768-1, the following information shall be indicated in or near the title block:
a) “ISO 2768”;
b) the tolerance class in accordance with ISO 2768-1;
c) the tolerance class in accordance with this part of ISO 2768.
EXAMPLE
ISO 2768-mk
In this case the general tolerances for angular dimensions in accordance with ISO 2768-1 do not apply to right angles (90°), which are implied but not indicated, because this part of ISO 2768 specifies general tolerances on perpendicularity.
6.2 If the general dimensional tolerances (tolerance
class m) shall not apply, the respective letter shall be omitted from the designation to be indicated on the drawing:
EXAMPLE
ISO 2768-K
In cases where the envelope requirement also applies to all single features of size1), the designation “E” shall be added to the general designation specified in 6.1:
EXAMPLE
ISO 2768-mK-E
NOTE The envelope requiremen cannot apply to features with individually indicated straightness tolerances which are greater than their size tolerances, e.g. stock material.
7 Rejection
Unless otherwise stated, workpieces exceeding the general geometrical tolerance shall not lead to automatic rejection provided that the ability of the workplace to function is not impaired
(see clause A.4).
1) For the purposes of this part of ISO 2768, a single feature of size comprises a cylindrical surface or two parallel plane surfaces.
© BSI 03-1999 5
EN 22768-2:1993
Annex A (informative)
Concepts behind general tolerancing of geometrical characteristics
A.1 General tolerances should be indicated on the drawing by reference to this part of ISO 2768 in accordance with clause 6.
The values of general tolerances correspond to grades of customary workshop accuracy, the appropriate tolerance class being selected and indicated on the drawing.
A.2 Above a certain tolerance value, which corresponds to the customary workshop accuracy, there is usually no gain in manufacturing economy by enlarging the tolerance. In any event, workshop machinery and the usual workmanship normally do not manufacture features with greater deviations. For example, a feature of 25 mm ± 0,1 mm diameter by 80 mm long manufactured in a workshop with a customary accuracy equal to or finer than
ISO 2768-mH contains the geometrical deviations well within 0,1 mm for circularity, 0,1 mm for straightness of surface elements, and 0,1 mm for circular radial run-out (the values given have been taken from this part of ISO 2768). Specifying tolerances would be of no benefit in this particular workshop.
However, if, for functional reasons, a feature requires a smaller tolerance value than the “general tolerances”, then that feature should have the smaller tolerance indicated individually adjacent to the particular feature. This type of tolerance falls out-side the scope of general tolerances.
In cases where the function of a feature allows a geometrical tolerance equal to or larger than the general tolerance values, this should not be individually indicated, but should be stated on the drawing as described in clause 6. This type of tolerance allows full use of the concept of general geometrical tolerancing.
There will be “exceptions to the rule” where the function allows a larger tolerance than the general tolerances, and the larger tolerance will provide a gain in manufacturing economy. In these special cases, the larger geometrical tolerance should be indicated individually adjacent to the particular feature, e.g. the circularity tolerance of a large and thin ring.
A.3 Using general geometrical tolerances leads to the following advantages:
a) drawings are easier to read and thus communication is made more effective to the user of the drawing;
b) the design draughtsman saves time by
avoiding detailed tolerance calculations as it is sufficient only to know that the function allows a tolerance greater than or equal to the general tolerance;
c) the drawing readily indicates which features can be produced by normal process capability, which also assists quality engineering by reducing inspection levels;
d) those features remaining, which have individually indicated geometrical tolerances, will, for the most part, be those controlling features for which the function requires relatively small tolerances and which therefore
may cause special effort in the production — this will be helpful for production planning and will assist quality control services in their analysis of inspection requirements;
e) purchase and subcontract supply engineers can negotiate orders more readily since the
“customary workshop accuracy” is known before the contract is placed; this also avoids arguments on delivery between the buyer and the supplier,
since in this respect the drawing is complete.
These advantages are fully obtained only when there is sufficient reliability that the general tolerances will not be exceeded, i.e. when the customary workshop accuracy of the particular workshop is equal to or finer than the general tolerances indicated in the drawing.
The workshop should, therefore,
— find out by measurements what its customary workshop accuracy is;
— accept only those drawings having general tolerances equal to or greater than its customary workshop accuracy;
— check by sampling that its customary workshop accuracy does not deteriorate.
Relying on undefined “good workmanship” with all its uncertainties and misunderstandings is no longer necessary with the concept of general geometrical tolerances. The general geometrical tolerances define the required accuracy of “good workmanship”.
A.4 The tolerance the function allows is often greater than the general tolerance. The function of the part is, therefore, not always impaired when the general tolerance is (occasionally) exceeded at any feature of the workpiece. Exceeding the general tolerance should lead to a rejection of the workpiece only if the function is impaired.
6 © BSI 03-1999
EN 22768-2:1993
Annex B (informative)
Further information
B.1 General geometrical tolerances
(see clause 5)
According to the principle of independency
(see ISO 8015), general geometrical tolerances apply independently of the actual local size of the workpiece features. Accordingly, the general geometrical tolerances may be used even if the
features are everywhere at their maximum material
size (see Figure B.1).
If the envelope requiremen is individually indicated adjacent to the feature or generally to all features of size as described in clause 6, this requirement should also be complied with.
B.2 Circularity (see 5.1.2) — Examples
EXAMPLE 1 (see Figure B.2)
The permissible deviation of the diameter is indicated directly on the drawing; the general tolerance on circularity is equal to the numerical value of the diameter tolerance.
EXAMPLE 2 (see Figure B.2)
The general tolerances in accordance with the
indication ISO 2768-mK apply. The permissible deviations for the diameter of 25 mm are ± 0,2 mm. These deviations lead to the numerical value
of 0,4 mm which is greater than the value of 0,2 mm given in Table 4; the value of 0,2 mm, therefore,
applies for the circularity tolerance.
B.3 Cylindricity (see note 2 in 5.1.3)
The combined effect of the general tolerances of circularity, straightness and parallelism is, for geometrical reasons, smaller than the sum of the three tolerances since there is also a certain limitation by the size tolerance. However, for the sake of simplicity, in order to decide whether the envelope requirement or an individual cylindricity tolerance is to be indicated, the sum of the three tolerances can be taken into account.
B.4 Parallelism (see 5.2.2)
Depending on the shapes of the deviations of the features, the parallelism deviation is limited by the numerical value of the size tolerance
(see Figure B.3) or by the numerical value of the straightness or flatness tolerance (see B.4).
Figure B.1 — Principal of independency; maximum permissible deviations on the same
feature
© BSI 03-1999 7
EN 22768-2:1993
Example Indication on the drawing
Values in millimetres
Circularity tolerance zone
B.5 Symmetry (see 5.2.4) — Examples
1
2
Figure B.2 — Examples of general tolerances on circularity
Figure B.3 — Parallelism deviation equal to the numerical value of the size tolerance
Figure B.4 — Parallelism deviation equal to the numerical value of the straightness tolerance
Figure B.5 — Example of general tolerances
on symmetry (datums specified in accordance with 5.2.4)
8 © BSI 03-1999
EN 22768-2:1993
B.6 Example of a drawing
NOTE 1 The tolerances shown in chain thin double-dashed lines (boxes and circles) are general tolerances. These tolerance values would be automatically achieved by machining in a workshop with a customary accuracy equal to or finer than ISO 2768-mH and would not normally require to be inspected.
NOTE 2 As some tolerances also limit the deviations of other characteristics of the same feature, e.g. the perpendicularity tolerance also limits the straightness deviations, not all general tolerance are shown in the interpretation above.
Figure B.6 — Example of general tolerances on a drawing
© BSI 03-1999 9
EN 22768-2:1993
Annex ZA (informative)
Normative references to international publications with their relevant
European publications
This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply
to this European Standard only when incorporated in it by amendment or revision. For undated references
the latest edition of the publication referred to applies (including amendments).
Publication Title EN/HD
ISO 1101 Technical drawings — Geometrical tolerancing — Tolerances
of form, orientation, location and run-out — Generalities, definitions, symbols, indications on drawings
ISO 2768-1 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
ISO 5459 Technical drawings — Geometrical tolerancing — Datums and datum-systems for geometrical tolerances
ISO 8015 Technical drawings — Fundamental tolerancing principle
EN 22768-1
10 © BSI 03-1999
BS EN 22768-2:1993
National annex NA (informative)
Committees responsible
The United Kingdom participation in the preparation of this European Standard was entrusted by the Machine, Engineers and Hand Tools Standards Policy Committee (MTE/-) to Technical Committee MTE/24, upon which the following bodies were represented:
British Cast Iron Research Association
British Electrical and Allied Manufacturers’ Association
British Foundry Association
Federation of British Engineers Tool Manufacturers
Railway Industry Association of Great Britain Society of British Aerospace Companies Ltd. Society of Motor Manufacturers and Traders Ltd. Zinc Development Association
Coopted members
© BSI 03-1999
BSI
389 Chiswick High Road
London
W4 4AL
|
|
|
|
|
|
| BSI ￐ British Standards Institution
|
|
|
|
|
|
| BSI is the independent national body responsible for preparing British Standards. It
|
| presents the UK view on standards in Europe and at the international level. It is
| incorporated by Royal Charter.
|
| Revisions
|
| British Standards are updated by amendment or revision. Users of British Standards
| should make sure that they possess the latest amendments or editions.
|
| It is the constant aim of BSI to improve the quality of our products and services. We
|
| would be grateful if anyone finding an inaccuracy or ambiguity while using this
| British Standard would inform the Secretary of the technical committee responsible,
| the identity of which can be found on the inside front cover. Tel: 020 8996 9000.
| Fax: 020 8996 7400.
|
| BSI offers members an individual updating service called PLUS which ensures that
| subscribers automatically receive the latest editions of standards.
|
|
| Buying standards
|
| Orders for all BSI, international and foreign standards publications should be
| addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001.
|
| In response to orders for international standards, it is BSI policy to supply the BSI
| implementation of those that have been published as British Standards, unless
| otherwise requested.
|
|
| Information on standards
|
| BSI provides a wide range of information on national, European and international
| standards through its Library and its Technical Help to Exporters Service. Various
| BSI electronic information services are also available which give details on all its
| products and services. Contact the Information Centre. Tel: 020 8996 7111.
| Fax: 020 8996 7048.
|
|
| Subscribing members of BSI are kept up to date with standards developments and
| receive substantial discounts on the purchase price of standards. For details of
| these and other benefits contact Membership Administration. Tel: 020 8996 7002.
| Fax: 020 8996 7001.
|
| Copyright
|
| Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of
|
| the publications of the international standardization bodies. Except as permitted
| under the Copyright, Designs and Patents Act 1988 no extract may be reproduced,
| stored in a retrieval system or transmitted in any form or by any means ﾱ electronic,
| photocopying, recording or otherwise ﾱ without prior written permission from BSI.
|
| This does not preclude the free use, in the course of implementing the standard, of
| necessary details such as symbols, and size, type or grade designations. If these
|
| details are to be used for any other purpose than implementation then the prior
| written permission of BSI must be obtained.
|
| If permission is granted, the terms may include royalty payments or a licensing
| agreement. Details and advice can be obtained from the Copyright Manager.
| Tel: 020 8996 7070.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
没有找到相关结果
已邀请:
RSS Feed
3 个回复
lipingtao_jay00 (威望:5) (广东 东莞) 计算机相关 其它
赞同来自: