>> P.198
QuickGuidetoPrecisionMeasuringInstrumentsMicrometerHeadsKeyFactorsinSelectionKeyfactorsinselectingamicrometerheadarethemeasuringrange,spindleface,stem,graduations,thimblediameter.Withreferencetothecontentofeachproduct,selectamicrometersuitedtothepurpose.■Stem•Thestemusedtomountamicrometerheadisclassiedasa"plaintype"or"clampnuttype"asillustratedabove.ThestemdiameterismanufacturedtoanominalMetricorImperialsizePlainstemwithanh6tolerance.•Theclampnutstemallowsfastandsecureclampingofthemicrometerhead.Theplainstemhastheadvantageofwiderapplicationandslightpositionaladjustmentintheaxialdirectiononnalinstallation,althoughitdoesrequiresasplit-xtureclampingarrangementoradhesivexing.•General-purposemountingxturesareavailableasoptionalaccessories.Stemlocknuttype■MeasuringFace•Aatmeasuringfaceisoftenspeciedwhereamicrometerheadisusedinmeasurementapplications.•Whenamicrometerheadisusedasafeeddevice,asphericalfacecanminimizeerrorsduetomisalignment(FigureA).Alternatively,aatfaceonthespindlecanbearagainstasphere,suchasacarbideball(FigureB).•Anon-rotatingspindletypemicrometerheadoronettedwithananti-rotationdeviceonthespindle(FigureC)canbeusedifatwistingactionontheworkpiecemustbeavoided.•Ifamicrometerheadisusedasastop,thenaatfaceonboththespindleandthefaceitcontactsprovidesdurability.FlatfaceSphericalfaceAnti-rotationdeviceFigureCFigureAFigureB■Non-RotatingSpindle•Anon-rotatingspindletypeheaddoesnotexertatwistingactiononaworkpiece,whichmaybeanimportantfactorinsomeapplications.■SpindleThreadPitch•Thestandardtypeheadhas0.5mmpitch.•1mm-pitchtype:quickertosetthanstandardtypeandavoidsthepossibilityofa0.5mmreadingerror.Excellentload-bearingcharacteristicsduetolargerscrewthread.•0.25mmor0.1mm-pitchtypeThistypeisthebestforne-feedorne-positioningapplications.3-65
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