ISO 5458:1998 download.Geometrical Product Specifications ( GPS ) – Geometrical tolerancing Positional tolerancing.
ISO 5458 is a geometrical product specification (GPS) standard and is to be regarded as a
general GPS standard (see ISO/TR 14638). It influences chain links 1 and 2 of the chain of standards on location.
For more detailed information of the relation of this standard to the GPS matrix model, see annex C.
ISO 5458 is intended to promote the relationship between the designer and the manufacturer.
The concept of positional tolerancing, as described in ISO 1101, is further elaborated in ISO 5458.
The figures in ISO 5458 serve to illustrate the subject matter only and are not necessarily complete.
Other relevant International Standards, such as those dealing with the maximum material requirement (ISO 2692), datums and datum systems (ISO 5459), should be taken into consideration when using ISO 5458.
For the purposes of ISO 5458, all dimensions and tolerances on the drawings have been shown in vertical lettering. It should be understood that these indications could just as well be written in free-hand or inclined (italic) lettering without altering the meaning of the indications.
For the presentation of lettering (proportions and dimensions), see ISO 3098-1.
1 Scope
ISO 5458 describes positional Ioterandng. This tolerancing method Is apped to the location of a point, of a line nominally SIT WghI and of a surface nominally plane, e.g. the centre of a sphere, the axis of a hole or shaft and the median surface of a slot.
NOTE Profile toteranong is used af’ien has we not wended to be slra4 or surfaces are not intended to lie i a plane see ISO 160.
2 NormatIve reference
The following standard contains provisions $tich, through reference in this text constitute provisions of this International Standard. At the time of publication, the edition indicated was valid Al standards are subect to revision, and parties to agreements based on ISO 5458 are encouraged to investigate the poss*likty of applying the most recent edition of the standard indicated below. MeiNers of lEG and ISO maintain registers of currently valid international Standards
ISO 1101:—”. Geometrical Product SpecificatIons (GPS) — GeometncaJ foerancuig — Generaldes, deflrWtsoos. symbols. IndicatIon on drawlngs
3 DefinItions
Definitions related to features are under development and will be issued as ISO 14660-1. This work will result in new terms that are different from those used in ISO 5458, These new terms are defined In annex A and appear in the main body of ISO 5458 in parentheses next to the currently used term.
4 Establishment of positional tolerances
4.1 General
The primary constituents are theoretically exact dimensions, tolerance zones and dalums
4.2 Fundamental requirement
Posthonal tolerances are associated with theoretically exact dimensions and define the limits for the location of actual (extracted features, such as points, axes, median surfaces. nominaly straight bnes and nominally plane surfaces relative to each other or In relation to one or more datums. The tolerance zone is symmetrically disposed gout the theoretically exact location,
NOTE POsiflonhi tc4eranoss do not accune wtien Eheoret4cdy exact mensaons are arranged in a ctain (see flgure 4). (ThiS contreets with menscnai tolerances that are arranged m a chen.) PositlonI lolerancing allows clear reference 10 be made to one or more delufln.
4.3 TheoretIcally exact dImensions
Theoretically exact dimensions, both angular and linear, are indicated by being enclosed In a rectangular frame in accordance with ISO 1101. This is Illustrated in flgures2a), 2 b), 3 a), 4 a), 5a) and7 a).
The theoretically exact dimensions 0 and 90, 180 or distance 0 between
— positionally toleranced features not related to a datum [see figure 4 a) and fIgure 5 a)J,
— positionally toteranced features related to the same datum(s) (see figure 2 afl.
— positionally toleranced features and lheU related datums (see fIgure 1).
are implied without speclhlc indication.
When the positional tolerance Ieatures share the same centrellrie or axis they are regarded as theoretically exacity related features, uriess otherwise specified, e.g. in relation to different datums or other reason indicated by an aptxoprlate note on the drawing as shown In figure 2 b).
4.4 Positional tolerances on a complete circle
When positionally toleranced features are arranged in a complete circle it is understood that the features are equally spaced, unless otherwise stated, and that their locations are theoretically exact.
If two or more groups of features are shown on the same axis, they shall be considered to be a single pattern when
— they are not related to a datum;
— they are related to the same datum or datum system (datums in the same order of precedence or under the same material conditions) [see figure 2 a)];
unless otherwise stated [see figure 2 b)].
4.5 Directions of positional tolerances
4.5.1 Positional tolerances In one direction only
The tolerance value can be specified in one direction. The orientation of the width of the tolerance zone is based on the pattern of the theoretically exact dimensions and is at 00 or 900 as indicated by the direction of the arrow line [see figures 3 a) and 3 b)j unless otherwise indicated.
5 Tolerance combinations
5.1 If a group of features is individually located by positional tolerancing and their pattern location is also located by positional tolerancing, each requirement shall be met independently [see figure 7 a)].
5.2 The actual (extracted) axis of each of the four holes shall lie within the cylindrical tolerance zone of diameter
0,01; the positional tolerance zones are located in their theoretically exact positions to each other and perpendicular to datum A [see figure 7 b)].
5.3 The actual (extracted) axis of each holes shall lie within the cylindrical tolerance zone of diameter 0,2; the positional tolerance zones are perpendicular to datum A and located in their exact theoretical positions in relation to each other and to the datums B and C [see figure 7 C)].