BS 978-1-1968 Fine pitch gears

BRITISHSTANDARDCONFIRMEDAUGUST1990BS978-1:1968IncorporatingAmendmentNo.1SpecificationforFinepitchgears—Part1:InvoluteSpurandHelicalGearsUDC621.833.1BS978-1:1968ThisBritishStandard,havingbeenapprovedbytheMechanicalEngineeringIndustryStandardsCommitteeandendorsedbytheChairmanoftheEngineeringDivisionalCouncil,waspublishedundertheauthorityoftheGeneralCouncilon31January1968©BSI10-1999FirstpublishedOctober1941FirstrevisionJanuary1952SecondrevisionNovember1962ThirdrevisionJanuary1968ThefollowingBSIreferencesrelatetotheworkonthisstandard:CommitteereferenceMEE/17,MEE/17/4Draftforcomment66/14936ISBN580000281Co-operatingorganizationsTheMechanicalEngineeringIndustryStandardsCommittee,underwhosesupervisionthisBritishStandardwasprepared,consistsofrepresentativesfromthefollowingGovernmentdepartmentsandscientificandindustrialorganizations:TheGovernmentdepartmentandscientificandindustrialorganizationsmarkedwithanasteriskintheabovelist,togetherwiththefollowing,weredirectlyrepresentedonthecommitteeentrustedwiththepreparationofthisstandard:AssociatedOffices’TechnicalCommitteeInstitutionofCivilEngineersAssociationofConsultingEngineers*InstitutionofGasEngineersAssociationofMiningElectricalandInstitutionofHeatingandVentilatingMechanicalEngineers*EngineersBoardofTradeInstitutionofMechanicalEngineersBritishChemicalPlantManufacturers’InstitutionofMechanicalEngineersAssociation(AutomobileDivision)BritishCompressedAirSocietyInstitutionofProductionEngineers*BritishElectricalandAlliedManufacturers’LocomotiveandAlliedManufacturers’Association*AssociationofGreatBritainBritishGearManufacturers’Association*LondonTransportBoardBritishInternalCombustionEngineMachineToolTradesAssociation*Manufacturers’AssociationMinistryofDefenceBritishIronandSteelFederationMinistryofLabour(H.M.FactoryInspectorate)BritishMechanicalEngineeringFederationMinistryofPowerBritishPumpManufacturers’AssociationMinistryofPublicBuildingandWorksCrownAgentsforOverseaGovernmentsandMinistryofTechnology—NationalAdministrationsEngineeringLaboratory*ElectricityCouncil,theCentralElectricityMinistryofTransportGeneratingBoardandtheAreaBoardsNationalCoalBoardinEnglandandWalesNationalPhysicalLaboratory(MinistryofEngineeringEquipmentUsers’AssociationTechnology)GasCouncilRadioIndustryCouncilInstituteofMarineEngineers*RoyalInstituteofBritishArchitectsBritishHorologicalInstituteMinistryofTechnologyElectronicEngineeringAssociationNavyandVickersGearingResearchInstituteofBritishFoundrymenAssociationInstitutionofEngineeringInspectionNorth-EastCoastInstitutionofEngineersInstitutionofEngineersandShipbuildersinandShipbuildersScotlandSocietyofMotorManufacturersandTradersMillingCutterandReamerAssociationLtd.MinistryofDefence,ArmyDepartmentUniversityofSheffieldMinistryofDefence,NavyDepartmentManufacturersoffinepitchgearsAmendmentsissuedsincepublicationAmd.No.DateofissueComments3305May1980IndicatedbyasidelineinthemarginBS978-1:1968©BSI10-1999iContentsPageCo-operatingorganizationsInsidefrontcoverForewordiii1General1.1Scope11.2Terminologyandnotation11.3Preferredrangeofnormaldiametralpitches21.4Basicracktoothprofile22Designdetails2.1Outsidediameterandcentredistance32.2Modificationofaddendumandcentredistance33Accuracyofgearblanksandgears3.1General133.2Dualflankcompositetesting143.3Limitsoftoleranceonblanksandgearelements154Limitsandtolerancesofassembly4.1Centredistance174.2Depthofengagement185InformationtobegivenondrawingsAppendixACentredistanceandaddendummodification21AppendixBExamplesofcalculations23AppendixCComparablediametralpitchesandmetricmodules29AppendixDSingleflankcompositetesting:Limitsoftolerance29AppendixECalculationofmeasuringpindimensionsforexternalandinternalspurgears29Figure1—Basicracktoothprofileforunitnormaldiametralpitch2Figure2—Basicracktoothprofileforunitnormaldiametralpitchwithbacklashallowance2Figure3—Limitingvaluesofaddendummodificationcoefficient5Figure4—Minimumpermissibleaddendummodificationcoefficientforhelicalpinions(!n=20°)6Figure5—Tolerancezoneforprofileerror15Figure6—Exampleofinformationtobegivenondrawings20Figure7—Chartfornormalbacklashwhenx1+x2=y28Table1—NormaldiametralpitchPn(inchunits)2Table2—Dataforspurpinionsofunitdiametralpitchhavingfewerthan17teeth4Table3—Centredistancesforspurgearpairsofunitdiametralpitchfortheconditionsgiveninclause2.2.47Table4—Forcesappropriatetothepitchsuitableforbrassandsteelproductgears14Table5—Limitsoftolerance14Table6—Limitsoftoleranceongearblanks15Table7—Limitsoftoleranceontoothprofile16Table8—Limitsoftoleranceonpitch16Table9—Limitsoftoleranceontoothalignment16BS978-1:1968ii©BSI10-1999PageTable10—Limitsoftoleranceonradialrun-outofteeth17Table11—Limitsoftoleranceontooththickness17Table12—Limitsoftoleranceoncentredistanceofmounting17Table13—Minimumdepthofengagementforspurgearpairswith28to33teeth(z2+z1)18Table14—Minimumdepthofengagementforspurgearpairswithmorethan33teeth(z2+z1)18BS978-1:1968©BSI10-1999iiiForewordThisstandardmakesreferencetothefollowingBritishStandards:BS978,Finepitchgears.BS978-2,Cycloidaltypegears.BS978-PD3376,AddendumNo.1