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BRITISH STANDARD
General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
The European Standard EN 22768-1:1993 has the status of a British Standard
UDC 621.713.12:744.4
BS EN 22768-1:1993 ISO 2768-1: 1989
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
BS EN 22768-1:1993
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 Belgium Denmark Finland Greece Iceland Ireland Italy Luxembourg Netherlands Norway Portugal Spain Sweden Switzerland United Kingdom
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 November 1993 © BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference MTE 24 Announced in BSI News, October 1993 ISBN 0 580 22604 2
Oesterreichisches Normungsinstitut Institut belge de normalisation Dansk Standardiseringsraad Suomen Standardisoimisliito, r.y. Association française de normalisation Deutsches Institut für Normung e.V. Hellenic Organization for Standardization Technological Institute of Iceland National Standards Authority of Ireland Ente Nazionale Italiano di Unificazione Inspection du Travail et des Mines Nederlands Normalisatie-instituut Norges Standardiseringsforbund Instituto Portuguès da Qualidade Asociación Española de Normalización y Certificación Standardiseringskommissionen i Sverige Association suisse de normalisation British Standards Institution
Amendments issued since publication Amd. No.
Date
Comments
BS EN 22768-1:1993 Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
Contents Cooperating organizations National foreword
Page Inside front cover ii
Foreword Introduction 1 Scope 2 General 3 Normative references 4 General tolerances 5 Indications on drawings 6 Rejection Annex A (informative) Concepts behind general tolerancing of linear and angular dimensions Annex ZA (normative) Normative references to international publications with their relevant European publications Table 1 — Permissible deviations for linear dimensions except for broken edges Table 2 — Permissible deviations for broken edges Table 3 — Permissible deviations of angular dimensions National annex NA (informative) Committees responsible National annex NB (informative) Cross-reference
© BSI 12-1998
2 3 3 3 3 3 4 4 5 6 4 4 4 Inside back cover Inside back cover
i
BS EN 22768-1:1993
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
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 22768-1:1993 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications, published by the European Committee for Standardization (CEN). It is identical with ISO 2768-1:1989 published by the International Organization for Standardization (ISO). This standard supersedes BS 4500-3:1973, which is withdrawn. A British Standard does not purport to include all the necessary provisions of a contract. s 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 6, 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 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EUROPEAN STANDARD
EN 22768-1
NORME EUROPÉENNE EUROPÄISCHE NORM
April 1993
UDC 621.713.12:744.4 Descriptors: Machine components, dimensional tolerances, angular tolerances, untoleranced dimensions, dimensional deviations, specifications
English version
General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications (ISO 2768-1:1989)
Tolérances générales — Partie 1: Tolérances pour dimensions linéaires et angulaires non affectées de tolérances individuelles (ISO 2768-1:1989)
Allegemeintoleranzen — Teil 1: Toleranzen für Längen- und Winkelmaße ohne einzelne Toleranzeintragung (ISO 2768-1:1989)
This European Standard was approved by CEN on 1993-04-15. CEN 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 are the national standards bodies of Austria, Belgium, Denmark, Finland, , , 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
Ref. No. EN 22768-1:1993 E
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Foreword In 1991, the International Standard ISO 2768-1:1989 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications was submitted to the CEN Primary Questionnaire procedure. Following the positive result of the CEN/CS Proposal, ISO 2768-1:1989 was submitted to the Formal Vote. The result of the Formal Vote was positive. 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 October 1993, and conflicting national standards shall be withdrawn at the latest by October 1993. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, , , Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom. NOTE The European references to international publications are given in annex ZA (normative).
2
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Introduction
2 General
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.
When selecting the tolerance class, the respective customary workshop accuracy has to be taken into consideration. If smaller tolerances are required or larger tolerances are permissible and more economical for any individual feature, such tolerances should be indicated adjacent to the relevant nominal dimension(s). General tolerances for linear and angular dimensions apply when drawings or associated specifications refer to this part of ISO 2768 in accordance with clauses 4 and 5. If there are general tolerances for other processes, as specified in other International Standards, reference shall be made to them on the drawings or associated specifications. For a dimension between an unfinished and a finished surface, e.g. of cast or forged parts, for which no individual tolerance is directly indicated, the larger of the two general tolerances in question applies, e.g. for castings, see ISO 80621).
1 Scope This part of ISO 2768 is intended to simplify drawing indications and it specifies general tolerances for linear and angular dimensions without individual tolerance indications in four tolerance classes. NOTE 1 The concepts behind the general tolerancing of linear and angular dimensions are described in annex A.
It applies to the dimensions of parts that are produced by metal removal or parts that are formed from sheet metal. NOTE 2 These tolerances may be suitable for use with materials other than metal. NOTE 3 Parallel International Standards exist or are planned, e.g. see ISO 80621) for castings.
This part of ISO 2768 only applies for the following dimensions which do not have an individual tolerance indication: a) linear dimensions (e.g. external sizes, internal sizes, step sizes, diameters, radii, distances, external radii and chamfer heights for broken edges); b) angular dimensions, including angular dimensions usually not indicated, e.g. right angles (90°), unless reference to ISO 2768-2 is made, or angles of uniform polygons; c) linear and angular dimensions produced by machining assembled parts. It does not apply for the following dimensions: a) linear and angular dimensions which are covered by reference to other standards on general tolerances; b) auxiliary dimensions indicated in brackets; c) theoretically exact dimensions indicated in rectangular frames.
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. of IEC and ISO maintain s of currently valid International Standards. ISO 2768-2:1989, General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications. ISO 8015:1985, Technical drawings — Fundamental tolerancing principle.
4 General tolerances 4.1 Linear dimensions General tolerances for linear dimensions are given in Table 1 and Table 2. 4.2 Angular dimensions General tolerances specified in angular units control only the general orientation of lines or line elements of surfaces, but not their form deviations. The general orientation of the line derived from the actual surface is the orientation of the ing line of ideal geometrical form. The maximum distance between the ing line and the actual line shall be the least possible value (see ISO 8015).
ISO 8062:1984, Castings — System of dimensional tolerances.
© BSI 12-1998
3
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
The permissible deviations of angular dimensions are given in Table 3.
EXAMPLE ISO 2768-m
5 Indications on drawings
6 Rejection
If general tolerances in accordance with this part of Unless otherwise stated, workpieces exceeding the ISO 2768 shall apply, the following information general tolerance shall not lead to automatic shall be indicated in or near the title block: rejection provided that the ability of the workpiece to function is not impaired (see clause A.4). a) “ISO 2768” b) the tolerance class in accordance with this part of ISO 2768. Table 1 — Permissible deviations for linear dimensions except for broken edges (external radii and chamfer heights, see Table 2) Values in millimetres Tolerance class Designation
Permissible deviations for basic size range a 0,5 up to 3
Description
over 3 up to 6
over 6 up to 30
over 30 up to 120
over 120 up to 400
over 400 up to 1 000
over 1 000 up to 2 000
over 2 000 up to 4 000
f
fine
± 0,05
± 0,05
± 0,1
± 0,15
± 0,2
± 0,3
± 0,5
—
m
medium
± 0,1
± 0,1
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
c
coarse
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
±3
±4
v
very coarse —
± 0,5
±1
± 1,5
± 2,5
±4
±6
±8
aFor nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 2 — Permissible deviations for broken edges (external radii and chamfer heights) Values in millimetres Tolerance class Designation
Permissible deviations for basic size range a 0,5 up to 3
Description
f
fine
m
medium
c
coarse
v
very coarse
over 3 up to 6
over 6
± 0,2
± 0,5
±1
± 0,4
±1
±2
aFor nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 3 — Permissible deviations of angular dimensions Tolerance class Designation
Description
Permissible deviations for ranges of lengths, in millimetres, of the shorter side of the angle concerned up to 10
f
fine
m
medium
c
coarse
v
very coarse ± 3°
4
over 10 up to 50
over 50 up to 120
over 120 up to 400
over 400
± 1°
± 0°30′
± 0°20′
± 0°10′
± 0°5′
± 1°30′
± 1°
± 0°30′
± 0°15′
± 0°10′
± 2°
± 1°
± 0°30′
± 0°20′
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Annex A (informative) Concepts behind general tolerancing of linear and angular dimensions A.1 General tolerances should be indicated on the drawing by reference to this part of ISO 2768 in accordance with clause 5. The values of general tolerances correspond to tolerance classes of customary workshop accuracy, the appropriate tolerance class being selected and indicated on the drawing according to the requirement for the components. A.2 Above certain tolerance values, there is usually no gain in manufacturing economy by enlarging the tolerance. For example, a feature having a 35 mm diameter could be manufactured to a high level of conformance in a workshop with “customary medium accuracy” Specifying a tolerance of ± 1 mm would be of no benefit in this particular workshop, as the general tolerance values of ± 0,3 mm would be quite adequate. 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 dimension defining its size or angle. This type of tolerance falls outside the scope of general tolerances. In cases where the function of a feature allows a tolerance equal to or larger than the general tolerance values, these should not be indicated adjacent to the dimension but should be stated on the drawing as described in clause 5. This type of tolerance allows full use of the concept of general tolerancing. There will be “exceptions to the rule” where the function of the feature allows a larger tolerance than the general tolerances, and the larger tolerance will provide manufacturing economy. In these special cases, the larger tolerance should be indicated individually adjacent to the dimension for the particular feature, e.g. the depth of blind holes drilled at assembly. A.3 Using general tolerances leads to the following advantages:
c) the drawing readily indicates which feature can be produced by normal process capability, which also assists quality engineering by reducing inspection levels; d) those dimensions remaining, which have individually indicated tolerances, will, for the most part, be those controlling features for which the function requires relatively small tolerances and which therefore may require 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 sub-contract 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.
a) drawings are easier to read and thus communication is made more effective to the 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;
© BSI 12-1998
5
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EN 22768-1:1993
Annex ZA (normative) 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 2768-2
General tolerances — Part 2: Geometrical tolerances for features without individual tolerances indications
EN 22768-2
ISO 8015
Technical drawings — Fundamental tolerancing principle
6
© BSI 12-1998
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BS EN 22768-1:1993 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
National annex NB (informative) Cross-reference Publication referred to
Corresponding British Standard
ISO 2768-1:1989
BS EN 22768-2:1993 General tolerance Part 2: Geometrical tolerances for features without individual tolerance indications
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
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BRITISH STANDARD
General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
The European Standard EN 22768-1:1993 has the status of a British Standard
UDC 621.713.12:744.4
BS EN 22768-1:1993 ISO 2768-1: 1989
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
BS EN 22768-1:1993
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 Belgium Denmark Finland Greece Iceland Ireland Italy Luxembourg Netherlands Norway Portugal Spain Sweden Switzerland United Kingdom
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 November 1993 © BSI 12-1998 The following BSI references relate to the work on this standard: Committee reference MTE 24 Announced in BSI News, October 1993 ISBN 0 580 22604 2
Oesterreichisches Normungsinstitut Institut belge de normalisation Dansk Standardiseringsraad Suomen Standardisoimisliito, r.y. Association française de normalisation Deutsches Institut für Normung e.V. Hellenic Organization for Standardization Technological Institute of Iceland National Standards Authority of Ireland Ente Nazionale Italiano di Unificazione Inspection du Travail et des Mines Nederlands Normalisatie-instituut Norges Standardiseringsforbund Instituto Portuguès da Qualidade Asociación Española de Normalización y Certificación Standardiseringskommissionen i Sverige Association suisse de normalisation British Standards Institution
Amendments issued since publication Amd. No.
Date
Comments
BS EN 22768-1:1993 Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
Contents Cooperating organizations National foreword
Page Inside front cover ii
Foreword Introduction 1 Scope 2 General 3 Normative references 4 General tolerances 5 Indications on drawings 6 Rejection Annex A (informative) Concepts behind general tolerancing of linear and angular dimensions Annex ZA (normative) Normative references to international publications with their relevant European publications Table 1 — Permissible deviations for linear dimensions except for broken edges Table 2 — Permissible deviations for broken edges Table 3 — Permissible deviations of angular dimensions National annex NA (informative) Committees responsible National annex NB (informative) Cross-reference
© BSI 12-1998
2 3 3 3 3 3 4 4 5 6 4 4 4 Inside back cover Inside back cover
i
BS EN 22768-1:1993
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
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 22768-1:1993 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications, published by the European Committee for Standardization (CEN). It is identical with ISO 2768-1:1989 published by the International Organization for Standardization (ISO). This standard supersedes BS 4500-3:1973, which is withdrawn. A British Standard does not purport to include all the necessary provisions of a contract. s 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 6, 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 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EUROPEAN STANDARD
EN 22768-1
NORME EUROPÉENNE EUROPÄISCHE NORM
April 1993
UDC 621.713.12:744.4 Descriptors: Machine components, dimensional tolerances, angular tolerances, untoleranced dimensions, dimensional deviations, specifications
English version
General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications (ISO 2768-1:1989)
Tolérances générales — Partie 1: Tolérances pour dimensions linéaires et angulaires non affectées de tolérances individuelles (ISO 2768-1:1989)
Allegemeintoleranzen — Teil 1: Toleranzen für Längen- und Winkelmaße ohne einzelne Toleranzeintragung (ISO 2768-1:1989)
This European Standard was approved by CEN on 1993-04-15. CEN 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 are the national standards bodies of Austria, Belgium, Denmark, Finland, , , 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
Ref. No. EN 22768-1:1993 E
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Foreword In 1991, the International Standard ISO 2768-1:1989 General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications was submitted to the CEN Primary Questionnaire procedure. Following the positive result of the CEN/CS Proposal, ISO 2768-1:1989 was submitted to the Formal Vote. The result of the Formal Vote was positive. 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 October 1993, and conflicting national standards shall be withdrawn at the latest by October 1993. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, , , Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom. NOTE The European references to international publications are given in annex ZA (normative).
2
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Introduction
2 General
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.
When selecting the tolerance class, the respective customary workshop accuracy has to be taken into consideration. If smaller tolerances are required or larger tolerances are permissible and more economical for any individual feature, such tolerances should be indicated adjacent to the relevant nominal dimension(s). General tolerances for linear and angular dimensions apply when drawings or associated specifications refer to this part of ISO 2768 in accordance with clauses 4 and 5. If there are general tolerances for other processes, as specified in other International Standards, reference shall be made to them on the drawings or associated specifications. For a dimension between an unfinished and a finished surface, e.g. of cast or forged parts, for which no individual tolerance is directly indicated, the larger of the two general tolerances in question applies, e.g. for castings, see ISO 80621).
1 Scope This part of ISO 2768 is intended to simplify drawing indications and it specifies general tolerances for linear and angular dimensions without individual tolerance indications in four tolerance classes. NOTE 1 The concepts behind the general tolerancing of linear and angular dimensions are described in annex A.
It applies to the dimensions of parts that are produced by metal removal or parts that are formed from sheet metal. NOTE 2 These tolerances may be suitable for use with materials other than metal. NOTE 3 Parallel International Standards exist or are planned, e.g. see ISO 80621) for castings.
This part of ISO 2768 only applies for the following dimensions which do not have an individual tolerance indication: a) linear dimensions (e.g. external sizes, internal sizes, step sizes, diameters, radii, distances, external radii and chamfer heights for broken edges); b) angular dimensions, including angular dimensions usually not indicated, e.g. right angles (90°), unless reference to ISO 2768-2 is made, or angles of uniform polygons; c) linear and angular dimensions produced by machining assembled parts. It does not apply for the following dimensions: a) linear and angular dimensions which are covered by reference to other standards on general tolerances; b) auxiliary dimensions indicated in brackets; c) theoretically exact dimensions indicated in rectangular frames.
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. of IEC and ISO maintain s of currently valid International Standards. ISO 2768-2:1989, General tolerances — Part 2: Geometrical tolerances for features without individual tolerance indications. ISO 8015:1985, Technical drawings — Fundamental tolerancing principle.
4 General tolerances 4.1 Linear dimensions General tolerances for linear dimensions are given in Table 1 and Table 2. 4.2 Angular dimensions General tolerances specified in angular units control only the general orientation of lines or line elements of surfaces, but not their form deviations. The general orientation of the line derived from the actual surface is the orientation of the ing line of ideal geometrical form. The maximum distance between the ing line and the actual line shall be the least possible value (see ISO 8015).
ISO 8062:1984, Castings — System of dimensional tolerances.
© BSI 12-1998
3
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
The permissible deviations of angular dimensions are given in Table 3.
EXAMPLE ISO 2768-m
5 Indications on drawings
6 Rejection
If general tolerances in accordance with this part of Unless otherwise stated, workpieces exceeding the ISO 2768 shall apply, the following information general tolerance shall not lead to automatic shall be indicated in or near the title block: rejection provided that the ability of the workpiece to function is not impaired (see clause A.4). a) “ISO 2768” b) the tolerance class in accordance with this part of ISO 2768. Table 1 — Permissible deviations for linear dimensions except for broken edges (external radii and chamfer heights, see Table 2) Values in millimetres Tolerance class Designation
Permissible deviations for basic size range a 0,5 up to 3
Description
over 3 up to 6
over 6 up to 30
over 30 up to 120
over 120 up to 400
over 400 up to 1 000
over 1 000 up to 2 000
over 2 000 up to 4 000
f
fine
± 0,05
± 0,05
± 0,1
± 0,15
± 0,2
± 0,3
± 0,5
—
m
medium
± 0,1
± 0,1
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
c
coarse
± 0,2
± 0,3
± 0,5
± 0,8
± 1,2
±2
±3
±4
v
very coarse —
± 0,5
±1
± 1,5
± 2,5
±4
±6
±8
aFor nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 2 — Permissible deviations for broken edges (external radii and chamfer heights) Values in millimetres Tolerance class Designation
Permissible deviations for basic size range a 0,5 up to 3
Description
f
fine
m
medium
c
coarse
v
very coarse
over 3 up to 6
over 6
± 0,2
± 0,5
±1
± 0,4
±1
±2
aFor nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant nominal size(s).
Table 3 — Permissible deviations of angular dimensions Tolerance class Designation
Description
Permissible deviations for ranges of lengths, in millimetres, of the shorter side of the angle concerned up to 10
f
fine
m
medium
c
coarse
v
very coarse ± 3°
4
over 10 up to 50
over 50 up to 120
over 120 up to 400
over 400
± 1°
± 0°30′
± 0°20′
± 0°10′
± 0°5′
± 1°30′
± 1°
± 0°30′
± 0°15′
± 0°10′
± 2°
± 1°
± 0°30′
± 0°20′
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Annex A (informative) Concepts behind general tolerancing of linear and angular dimensions A.1 General tolerances should be indicated on the drawing by reference to this part of ISO 2768 in accordance with clause 5. The values of general tolerances correspond to tolerance classes of customary workshop accuracy, the appropriate tolerance class being selected and indicated on the drawing according to the requirement for the components. A.2 Above certain tolerance values, there is usually no gain in manufacturing economy by enlarging the tolerance. For example, a feature having a 35 mm diameter could be manufactured to a high level of conformance in a workshop with “customary medium accuracy” Specifying a tolerance of ± 1 mm would be of no benefit in this particular workshop, as the general tolerance values of ± 0,3 mm would be quite adequate. 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 dimension defining its size or angle. This type of tolerance falls outside the scope of general tolerances. In cases where the function of a feature allows a tolerance equal to or larger than the general tolerance values, these should not be indicated adjacent to the dimension but should be stated on the drawing as described in clause 5. This type of tolerance allows full use of the concept of general tolerancing. There will be “exceptions to the rule” where the function of the feature allows a larger tolerance than the general tolerances, and the larger tolerance will provide manufacturing economy. In these special cases, the larger tolerance should be indicated individually adjacent to the dimension for the particular feature, e.g. the depth of blind holes drilled at assembly. A.3 Using general tolerances leads to the following advantages:
c) the drawing readily indicates which feature can be produced by normal process capability, which also assists quality engineering by reducing inspection levels; d) those dimensions remaining, which have individually indicated tolerances, will, for the most part, be those controlling features for which the function requires relatively small tolerances and which therefore may require 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 sub-contract 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.
a) drawings are easier to read and thus communication is made more effective to the 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;
© BSI 12-1998
5
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
EN 22768-1:1993
Annex ZA (normative) 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 2768-2
General tolerances — Part 2: Geometrical tolerances for features without individual tolerances indications
EN 22768-2
ISO 8015
Technical drawings — Fundamental tolerancing principle
6
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
BS EN 22768-1:1993 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
National annex NB (informative) Cross-reference Publication referred to
Corresponding British Standard
ISO 2768-1:1989
BS EN 22768-2:1993 General tolerance Part 2: Geometrical tolerances for features without individual tolerance indications
© BSI 12-1998
Licensed copy: University of Auckland Library, University of Auckland Library, Version correct as of 15/07/2012 07:51, (c) The British Standards Institution 2012
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