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1 COMMITTEE DRAFT ISO/CD COMMITTEE DRAFT Date Supersedes document ISO/TC 213/WG 12 N 17 Reference number ISO/TC 213 /SC N 277 WARNING: This document is not an International Standard. It is distributed for review and comment. It is subject to change without notice and may not be referred to as an International Standard. ISO/TC 213/SC Title Dimensional and geometrical product specifications and verification Secretariat DS Circulated to P- and O-members, and to technical committees and organizations in liaison for: discussion at [venue/date of meeting] comments by [date] approval for registration as a DIS in accordance with of part 1 of the ISO/IEC Directives, by [date] (P-members vote only: ballot form attached) P-members of the technical committee or subcommittee concerned have an obligation to vote. Title (English) Geometrical product specification (GPS) - Linear and angular dimensioning and tolerancing: +/- limit specifications - Step dimensions, distances, angular sizes and radii Title (French) Spécification géométrique des produits (GPS) -... Reference language version: English French Russian Introductory note This Committee Draft was prepared by ISO/TC 213/WG 12 and has been submitted for ballot according to ISO/TC 213 Resolution 334 (Sydney 22/1999). Copyright notice This ISO document is a committee draft and is copyright protected by ISO. While the reproduction of committee drafts in any form for use by participants in the ISO standards development process is permitted without prior permission from ISO, neither this document nor any extract from it may be reproduced, stored or transmitted in any form for any other purpose without prior written permission from ISO. Requests for permission to reproduce this document for the purpose of selling it should be addressed to the secretariat indicated above or to ISO s member body in the country of the requester. Reproduction for sales purposes may be subject to royalty payments or a licensing agreement. Violators may be prosecuted. ISO 1999 All rights reserved FORM 7 (ISO) Version/V97.1.2

2 ISO/PDTR ISO Contents 1 Scope Normative references Definitions Linear dimensioning Step dimensioning Distance Distance between integral feature (plane surface) and derived feature Distance between two derived features Angular size Tolerances Step dimension with + and/or - deviation specifications Linear distance with + and/or - limit deviation specifications Angular size with + and/or - limit deviation specifications Radius with + and/or - limit deviation specifications Reference on drawings... 7 Annex A (informative) Cases where + and/or - limit deviation specifications should not be applied... 9 Annex B (informative) Relation to the GPS matrix model Copyright notice This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted under applicable laws of the user's country, neither this ISO draft nor any extract from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, photocopying, recording or otherwise, without written permission being secured. Requests for permission to reproduce should be addressed to ISO at the address below or ISO's member body in the country of requester. Mr. Hans Henrik Køster Secretariat of ISO/TC 213 Kollegievej 6 DK-2920 Charlottenlund DENMARK tel fax hhk@ds.dk Web Reproduction may be subject to royalty payments or a licensing agreement. Violators may be prosecuted. ii

3 ISO ISO/PDTR Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. The main task of technical committees is to prepare International Standards, but in exceptional circumstances a technical committee may propose the publication of a Technical Report of one of the following types: Type 1, when the required support cannot be obtained for the publication of an International Standard, despite repeated efforts, Type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard, Type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard ( state of the art, for example). Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be reviewed until the data provided are considered to be no longer valid or useful. This document is issued in the type 3 Technical Report series of publications (according to subclause G of ISO/IEC Directives - Part 1: Procedure, 1995) iii

4 ISO/PDTR ISO Introduction This International Standard is a geomertical produkt specification (GPS) standard and is to be regarded as a general GPS standard (see ISO/TR 14638). It influences the chain link 1 and 2 of the chains of standards on size, distance, radius and angle. For more detailed information of the relation of the standard to other standards and the GPS matrix model see annex B ISO contains general rules for dimensioning and dimensional tolerancing with + and/or - limit deviations specified in technical drawings. These rules are not always sufficient for an unambiguous description of the workpiece geometry, for example: Distances between axes of holes on a pitch cylinder can not be toleranced by + and/or - limit deviation specifications suitable for the function. See Figure A.1 left. Angles between planes containing axes of holes can not be toleranced by + and/or - limit deviation specifications suitable for the function. Often the same applies for angles between more than one median planes, when they are represented by only one centre line on the drawing. See Figure A.4, A.5. Linear dimensions and + and/or - limit deviation specifications, even when they are related to the same reference (having the same origin as in superimposed running dimensioning) but dimensioned in two or three directions nominally perpendicular to each other are ambiguous. This is because it cannot be indicated in which order the surfaces must be considered. See Figure A.1 center, right. See also ISO TR XXXXX ((ISO/TC 213/AG 7 N 23)). Therefore ISO/TC 213 Geometrical Product Specification and Verification recommends to use + and/or - limit deviation specifications for features of size (e.g. cylinder and two oppsite parallel planes connected by a size dimension), see ISO XXXXX ((N3)). Other dimensions should preferably be indicated and toleranced according to the priciples given in ISO 1101 and related standards (e.g. by positional tolerancing), see ISO TR 1 X ((N2)). In certain cases (e.g. for step dimensions) the funcion (e.g. assembly) allows larger tolerances for the form (e.g. flatness) than for the location of the point of the surface which is most outward of the material. In these cases the production process (e.g. casting, forging, sheet metal working) becomes more economical when + and/or - limit deviation specifications are applied. For these and similar cases + and/or - limit deviation specifications for step dimensions, see 4.1, distances between an integral feature and a derived feature, see 4.2.1, distances between two derived features, see angular sizes, see 5 radii, see 6.4 are defined in this International Technical Report. iv

5 COMMITTEE DRAFT ISO ISO/PDTR Geometrical product specification (GPS) Linear and angular dimensioning and tolerancing: ± limit specified deviations Step dimensions, distances, angular sizes and radii 1 Scope This International Technical Report contains definitions for + and/or - limit deviation specifications of step dimenstions, distances, angular sizes and radii. NOTE This Technical Report shall be referred to on the drawing when it is used. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard 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 129:1985, Technical drawings Dimensioning General principles, definitions, methods of execution and special indications ISO 1101:1983, Technical drawings Geometrical tolerancing Tolerancing of form, orientation, location and run-out Generalities, definitions, symbols, indications on drawings ISO :1989, General tolerances Part 2: Geometrical tolerances for features without individual tolerance indications ISO/DIS :1996, Geometrical Product Specification (GPS) Geometric features Part 1: General terms and definitions ISO TR 1 XXX ((ISO/TC 213/AG 7 N 23)) 3 Definitions For the purpose of this Technical Report, the definitions of ISO , ISO 129, ISO 1101 and ISO 5459 apply. 4 Linear dimensioning Linear dimensioning may be applied for tolerancing sizes and distances between two ideal features, otherwise ISO 1101 shall be used. 4.1 Step dimensioning The step dimensioning is the distance between two parallel integral features (plane surfaces) which have the same direction outward of the material (see Figure 1). 1

6 ISO/PDTR ISO Figure 1 One of the two parallel plane surfaces is to be taken as the reference. The step dimension is the distance between the reference and the contacting associated feature which is parallel to the reference (see Figure 2). For the reference the definition of datums according to ISO 5459 apply. When there is indicated the origin symbol according to ISO 129 to one feature this feature applies as the reference feature only. See Figure 3. When there is no reference indicated (dimension line with arrows on both sides) both reference possibilities apply. NOTE 1: Form and orientation of the features are to be controlled by individually indicated geometrical tolerances or general tolerances of form (e.g. flatness) and of orientation (e.g. parallelism, perpendicularity). NOTE 2: This definition of the step dimensioning corresponds with the measuring method with a height gauge and reflects the functional requirements of the assembly. Drawing indication: Explanation: Reference possibility 1 Reference possibility 2 Figure 2 Step dimension 2

7 ISO ISO/PDTR Drawing indication: Explanation: Figure 3 Step dimension with origin symbol according to ISO Distance Distance between integral feature (plane surface) and derived feature See Figure 4. Figure 4 Distance between integral feature and derived feature One of the features is to be taken as a reference. The distances are determined by the range of the distances between the reference and the contacting associated feature of the other feature in any section plane perpendicular to the reference over the length of the extracted derived feature or over the length of the extracted plane feature. For the reference and for the contacting associated features the definition of datums according to ISO 5459 apply. The length of the extracted derived feature and the length of the extracted plane feature is determined by the distance of the contacting associated features to the adjacent surfaces. See Figure 5. When there is indicated the origin symbol according to ISO 129 to one feature this feature applies as the reference feature only. When there is no reference indicated (dimension line with arrows on both sides) both reference possibilities apply 3

8 ISO/PDTR ISO Drawing indication: Explanation: Reference possibility 1 Reference possibility 2: Figure 5 Distance between integral feature and derived feature Distance between two derived features See Figure 6 Figure 6 Distance between two derived features One of the features is to be taken as a reference. The distances are determined by the range of the distances between the reference and the derived contacting associated feature of the other feature in any section plane perpendicular to the reference over the length of the extracted derived feature. The length of the extracted derived feature is determined by the distance of the contacting associated features to the adjacent surfaces. See Figure 7. For the reference and for the contacting associated features the definition of datums according to ISO 5459 apply. 4

9 ISO ISO/PDTR When there is indicated the origin symbol according to ISO 129 to one feature this feature applies as the reference feature only. When there is no reference indicated (dimension line with arrows on both sides) both possibilities apply. NOTE 1: Form of the features are to be controlled by individual indicated or general form tolerances (e.g. flatness or cylindritciy). NOTE 2: In case of holes this definition of distance corresponds with the measuring method with the aid of inspection mandrels and suits to some functional requirements. Drawing indication: Explanation: Reference possibility 1: Reference possibility 2: Figure 7 Distance between two derived features 5

10 ISO/PDTR ISO 5 Angular size Angular dimensioning may be applied for tolerancing cones or wedges, otherwise ISO 1101 shall be used. Angular size of a cone or wedge. See Figure 8. Figure 8 Angular sizes Angle between two straight lines contacting the extracted feature in a section plane. The straight lines in the section plane are so oriented that the maximum distance to the extracted feature line is a minimum. The section plane is so oriented that the maximum angle occurs. See Figure 9. Drawing indication: Explanation: Figure 9 Angular size NOTE 1: NOTE 2: Form of the features are to be controlled by individually indicated or general form tolerances (e.g. flatness). The definition of the angular size corresponds with the measuring method with a protractor. NOTE 3: The definition of the angular size corresponds with the definition in ISO NOTE 4: Angular distance between a derived feature and another feature: see Annex A.2. 6 Tolerances 6.1 Step dimension with + and/or - deviation specifications The tolerance is the difference between the maximum and the minimum permitted step dimension. 6.2 Linear distance with + and/or - limit deviation specifications The tolerance is the difference between the maximum permitted linear distance and the minimum permitted linear distance. 6

11 ISO ISO/PDTR When the centre line on the drawing represents more than one derived feature (axes, median planes) the tolerance applies to all possible distances of two features each. 6.3 Angular size with + and/or - limit deviation specifications The tolerance is the difference between the maximum and the minimum permitted angular size. 6.4 Radius with + and/or - limit deviation specifications See Figure 10. Figure 10 Radius The feature must fit within the arcs of the maximum and minimum radii in section planes. The section planes are so oriented that the minimum radius occurs. To fit within the arcs means: For an outer feature: The extracted feature must contact the maximum radius arc at the zenith region and the minimum radius arc at the side regions. For an inner feature: The extracted feature must contact the maximum radius arc at the side regions and the minimum radius arc at the zenith region. See Figure 11. Outer feature Inner feature Figure 11 Radii + and/or - limit deviations NOTE 1: If necessary the three dimensional form of the feature is to be controlled by individually indicated or general form tolerances. NOTE 2: The definition of the radius + and/or - limit deviation corresponds with the inspection method with templets. 7 Reference on drawings When this Technical Report shall be applied the drawing shall have the title block indication: ISO/TR

12 ISO/PDTR ISO NOTE: Figure 12. This tolerancing allows features which fulfill the requirements given above and have the form as shown in Drawing indication: Explanation: Figure 12 Permissible shape of a feature with + and/or - limit specifications for the radius 8

13 ISO ISO/PDTR Annex A (informative) Cases where + and/or - limit deviation specifications should not be applied A.1 Linear distances between more than two features of size Distances between more than two features of size functional related to each other should be toleranced by positional tolerancing according to ISO 5458 and not be toleranced by + and - limit deviation specification for the following reasons: The + and - limit deviation specification do not limit the deviations of the extracted derived features (actual axes) from their common pitch cylinder or their common pitch planes and the right angles between the pitch planes, see Figure A.1 Figure A.1 Distances within a pattern of more than two features of size Furthermore, + and - limit deviations do not allow to distinguish between the individual derived features (actual axes) commonly represented by the centre line on the drawing although the function may allow different tolerances, see Figure A.2. Figure A.2 Distance of features of size represented by the same centre line on the drawing + and - limit deviation specifications do not give the possibility to refer to a datum system which may be necessary for functional reasons. 9

14 ISO/PDTR ISO + and - limit deviation specifications do not give the possibility to specify cylindrical tolerance zones which occur by the function of a fit of cylindrical parts and which are 57 % larger than the tolerance zones of + and - tolerancing. + and - limit deviation specifications do not give the possibility to specify which allow increasing tolerances under certain conditions. A.2 Angular distance of a feature of size Angles between features of size or between a feature of size and a plane feature, see Figures A.3 and A.4, should be toleranced according to ISO 1101, e.g. by positional tolerancing and not be toleranced by + and - limit deviation specification for the following reason: Angular distances need to determine a primary and a secondary datum establishing the apex of the angle. Figure A.3 Angular distance between an feature of size and a plane feature Figure A.4 Angular distance between features of size In the example of Figure A.5 it is not clear which features determine the horizontal leg of the angle and which pair of features determine the location of the apex. Figure A.5 Angular distance, ambiguous 10

15 ISO ISO/PDTR Annex B (informative) Relation to the GPS matrix model For full details about the GPS matrix model see ISO/TR B.1 Information about the standard and ist use ISO specifies... [to be completed] B.2 Position in the GPS matrix model This International Standard is a general GPS standard, which influences the chain link 1 and 2 of the chains of standards on size, distance, radius, angle in the general GPS matrix, as graphically illustrated in figure B.1 Global GPS-standards Fundamental GPS standards General GPS-standards Chain link number Size X X Distance X X Radius X X Angle X X Form of a line independent of datum Form of a line dependent of datum Form of a surface independent of datum Form of a surface dependent of datum Orientation Location Circular run-out Total run-out Datums Roughness profile Waviness profile Primary profile Surface imperfections Edges Figure B.1 B.3 Related standards The related standards are those of the chains of standards indicated in figure B.1. 11

16 ISO/PDTR ISO Bibliography ISO/TR 14638:1995, Geometrical Product Specifications (GPS) - Masterplan 12