Partie 2. Cotation et tolerancement-Remandations Pratique du dessin industriet
Technische Zelchnungen Teil 2.Empfehlungen fiur die BemaBung und Toterierung
BritishStandardsInstitution
BritishStandard Engineeringdrawingpractice
Part2.Remendationsfordimensioningand tolerancingofsize
T
Contents
PageCommittees responsible Back cover 3
21Dimnsit nd oflader in teminting surface22 Dimensioning small features putanpd p 624Inicaionofafturenotdrwntocae dimensions25Orlenthdednaxilierydiin 26Applicatnofaxilarydimenions27 Dimensionsrepeated to avoid longand interecting leodersZ8Notes andsymols sed toavoidlong and intersecting leaders30 Superimposedrunning dimensins 29 Parallel dimensioning31Chsin dimensioning 32 Combined dimensioning34 Diensinng byrdineandata 33 Dimensioning by coordinates35Dimentionsof diameters placed on themost appropriateviewforclarity36Diensionsrelted tfeture by leader lnes 37 Dimensioning concentric diameter on partial38 Dimensioningcircles views40 Dimensioningradll of arcs 39 Soherical diameters41Locating inconveniently placed centres44 Dimnsioning curved lines by means of radi 42 Indicating radiby other dimensions 43Sphericalrodius45 Dimensioning of curved lines bymeans of46 Dimensioning holes coordinates47Dimesioning holepositions onacrceby anguler specing48 Dimensioning hole positions by centre distancet or coordinates49Dimensioningoncurved surfaces 50Dinsiningofeqallyspaced fetures51Dingqullyacedfeus emphasising spacing52 Dimensioning of eguallspaced features onan arc53 Omissionldimensions where spaing are self-evidentaqunu Aq sn peeAenb u 9 required55Dimesiningrepeated fetures 56 Chamfers at 45 °57 Cnamters at angles other than 45* 58 Dimensioning of counterinks59Dimensioning of counterbores 60 Dimensioning of spottaces61Dinsningspcialscrwth 6Z Dimensioning to endoffulthread63 Dimensioning to end of futl thread and to timit of thread run-out64 Dimensioning threaded holes 65 Dimensioning keyways
Foreword
Remendations
1Scope 2 Definitions 5 54Methodofapplioation(gonerelcontions） 3 Principtes of dimensioning 55Arrangment of dimensionsand application of6 Dimensioning methods 7Methods of dimensioning mon features values !! 148 Toleranced dimensiors Intorpretation of toleranced oentre distances 17 2810 Dimensioning and tolerancing f taered 3111Interpetationflitsfsizefrthontrol features 3212Comletenes ofdrawinginreprtf of form 3713 Machiningandsuracetextureindication 14Marking tolerances 38 3943
Appendix
AAspects ofengineering grawing practice coveredby Britishndinternetionl(iISOstanderds
Index
Table
1Symbols for the direction of lay
Figures
1Appliation of dimensions to suit functionel2 Effect of changing datum surfaoes from those requirements3 Elements of dimensioning determined by functina requirements5Projection lines perpendioular torequired 4 Projection tines from points of intersectionProjetionlinlquetofete dimensions7Chord 8Arc10 Dimensioning interrupted features Angles11Dimensontines on partiat vie of asymmetrica part13Dimensioning sing oblique trokes where sce 12 Dimensioning where space is restricted14 Use of ettersnd symbots with dimensions is restricted15 Orientation of linear dimensions 16 Orientation ofangular dimensions17 Position of dimensions 18 Offset dimension19Arrangement fimensionsto void conestin 20 Use of an extension to a dimension line
Page
84 Atenatvmethodsoftlernngtpred 83Definingataperbyrefreetg 96object where the location ofa datum diameter is more important than the taper 3685Defininga taper byrefrnce toitsmating ponent 3786lnteretifliits fizwihdedeny of size and form 3787 Interpretations using the principleof independency for cylindrical ponentdrawing which has tolerances of size only given on the88 Surface texture symbols 89 Application of basic surface texture symbols 39 3901Applictonofrfectexturls 90Indictionfllowalesufaetexue 40 4092Applicationof surface texture valuesby reference letters and listed values 4093 Machiningnotpemied 94 Positionsforspecifyingadditional characteristics 41 4195Supplementarysurfacetextrehaecteristis and finishes96 Indication of sampling length 97 Direction of lay 41 4198 Method of identifying independency systemf 42tolerancing 43
Specifying a size with limits of tolerance Limits of size specified directlyInterpretationofengular tolerances Toterancing angutar dimensions1Comparison of chain and paratlel methods ot )Examples of general tolerance notes?An interpretation of toleranced centre distances dimensioning using toleranced centre distences3 Dimensioning positions by toteranced centre distances1Dimensions defining tapered objects Tolerancing a tapered object by the basic taperToierancing a tapered object by the basic taper {or angle) methodTolerancingtaperedobjetbythbaictapr {or angle) method using a detum distanoe1Besic teper (or angle) method of tolerancing (or angle) method usng a datum diameter3 Basic taper (or angle) method of tolerancing gradual or slow internal tapersponents where tapered festures need clearance on assembly）Basic taper (or angle) method of tolerancing a fast.taper1 Basic taper [or angle) method of tolerancing mating tepers thet determine longitudinalTolerancing tapered objects where the rate of locationtaper ismore important then size or location
Foreword
Thisrevisin ofBS308:Pert2hebeenprpred under the direction of the General Mechanical EngineeringStandards Committee;itreflectstheestablished conventionsand also takes account of both netional end international developments since the 1972 revision which is nowwithdrawn
The proven record of standards apotied to engineeringdrawingowenablesitrecognitionasthegraphicalanguage of munication in engineering both nationally andone country when bad on standards publihed by theInternational Organization for Standardization (ISO1 are understood and can be used around the world invirtullyll utris.Withthiinmindit wesregized and accepted to be important as a policy for this revisionquality of content of both text and figures to ensure their on pied aq pinous aes pu uoe noed eclarity and ease of understanding.
The UK continues to participate actively in ISO TechnicalCommittees on technical drawing for the establishmentof international published standards and much of the contents of this standerdreflectsthose agreementsreachedinterationallywithwhichtheUKhonurredom notes appear in this standard to draw attantion to oocasionatdivergecefpractceAppendxprovidesinomtin Aqpo d oseBritish and international standards.
The remendations of this standard have been octablichedhevingregardttherequrementsfmcrofingDrwins preparedinaccordncwiththisstndard should be witableformicrofimingandreduced-sizereproduetin techniqu
Duringthouef thisrevitinprulatttiohbeen peid to developments in puter aidedmachine draughting and it hes been established that such machinesare currently capable of plying with this standard. dsystem would not be expected to prejudice the under- stanging of a drawing otherwise claimed to ply withthis stenderd
main peridf transitinofUKindusty to themetric The 1972 revision was coincldentally undertaken during thesystemandalimitedrecognitionoftheimperialsystemof units wes inluded but thishas not been retalned In thepresent revision.
In the ISO mittee for technical drawing it is theconentiosfldisiplinessingtchildrwingand intention to unty nne setfstandadseractiesndtheir standards currently attempt to reflect that policy.
In the UKthe tracitionat separationsaremaintained and it should be carefully noted thet BS 308 continues to provide remendations fprengineringdrawingsinthemanufacturingindustriesassociate wih mechanicalelectrical lectronics hydraulics pneumatisand nuctear engineering disciptines as previously.
Thereuirementsf teuidingaritcturallndcontinue to be covered by BS1192.BS308 doenot cver structuralengineering and construction servicesindustries
speciel disciplines such as In naval architecture andsome industries usingBS308asabaisbutquiring aronautical lfingThretndardspuliedfothedisciplineBS4301 whichgivesremendations for additionalreendationsand conventions particular tosystemsndS2774whichgvesdrawingconventionsfr the preparation of drawings for optical elements andlaboratory glassware are examples.
S5070dngininrigdirmdrngtisaninstandrdtoBS308andcatersforthme industries providing remendations on a wide variety ofq called a drawing' and a drawing can be called a 'diagram' thestanddS308overwhtreommonlycepted it is useful to summerize the difference in the scopes ofto be drawings that define shape size and form.BS 5070flow ofone sort oranother and whichrelete ponents usuelly indicated by symbols)functionally one to another by the covers the drawring ofdlagrams that are normatly associated withfdhizneither do they in general indicate actual connections or locations.
precedent estalihed in1972of pulishing inthreePas. ForconniecefusethsrevisionfB308follwsthe
This Partleads onfrom Part 1 whichdeals withgeneral principles nd oontinues the development of the drawingwiththeapplicatinofdimensions and tolerance and other related normtiononsizeandfinishItatso coversinterpretations and toleranoing principles.
Therecdetioeregeerllyccordncewiththefollowing international standards.
ISO 406-1982 ISO 129-1985 Engineering drawing Dimensioning Tochnical drawings Liner enddrawings angular tolerancing Indications onISO 1302-1978 Technical drawings Method ofindicating surface textureondrwing
tolerancing. Particular attention is drawn to the revision of the clause oninterpretationf limits of size clause 9 of BS 308:Part 2: 1972hsslerewiha cariticationof the traditional interpretationanew tolerancing concept has benintroduced in which specifiedindependently (see 11.3).This principte ot independency.as it is known has ben developed internationally and is the subject of ISO 8015 in the drafting af which the UK hascolleborated It is to be noted however that wheres ISO 8015 willessentially specify the new conoept withonly concessionary reference to the monly accepted relationhp between tolerenceof size and formhe Sdrafting mittee has deemed it necessary that BS 308presents both concepts with equal status
Compllance witha British Standard does not of itselfconfer immunity from legal obligations.
Notes on the presentation of this standard
NOTE 1 The figures in this standard are independent andeach is selected solely for its simplicity and clarity tonqumep um uos nao o sadexa only possible examples and they are not intended as designotherwiseeredrewnaccordingto the besicremendations of this standard.
NOTE 2. Linear dimensions shown in the figures are inmiltimetres.
NOTE 3.Numerical values of dimensions and tolerancesgiveninthefigures throughoutare erbitrerily chosen to assist inillustrating the point under consideration;they aretypical and are not given as remendations.
NOTE 4.In the Iflustrations to this standard a conventionis adopted of using capital letters for notes that would apperaspartf therawing andlwercaeletersaresedfor notes explaining the point under consideration in reietion to the text.
NOTE5Thistaardreogizesbot th fit andtrofBS308:Part1:1984 as does ISO1281982.The first angle projction methods as having equal status see clause7angleprojectionmethod is thetnormally used for British Standards and is thus used in this publication in the interestsof uniformity of presentationThe third angle method is only shown whereitilustrates the relevant clus.However it should be understood that the alternative projection methodthrd angleprojectoncould equallywellhavebeen used without prejudice to the prineiples establishad.
NOTE 6.Due to the limitations of size of the figures in thisremendations of 5.4 in BS 308 : Part 1 : 1984. standard the sizes of arrowheads may not conform to the
