>> P.198
QuickGuidetoPrecisionMeasuringInstrumentsMicrometerHeadsKeyFactorsinSelectionKeyfactorsinselectingamicrometerheadarethemeasuringrange,spindleface,stem,graduations,thimblediameter,etc.Selectthemicrometerthatbestsuitsyourpurposebyreferringtoitsparticularcharacteristics.■Stem•Thestemusedtomountamicrometerheadisclassiedasa"plaintype"or"clampnuttype"asillustratedabove.ThestemdiameterismanufacturedtoanominalMetricorImperialsizePlainstemwithanh6tolerance.•Theinstallationsmethodhavethefollowingfeatures:•Clampnutstem:Allowsfastandsecureclampingofthelineargagehead.•Plainstem:Widerrangeofapplicationwithpositionaladjustmentintheaxialdirectiononnalinstallation,butrequiresasplit-xtureclampingarrangementoradhesivexing.•General-purposemountingxturesareavailableasoptionalaccessories.■MeasuringFace•Aatmeasuringfaceisoftenspeciedwhereamicrometerheadisused.•Whenamicrometerheadisusedasafeeddevice,asphericalfacecanminimizeerrorsduetomisalignment(FigureA).Alternatively,theatfaceandsphericalfacecanbereversedsothatthespindlecanbearagainstasphere,suchasacarbideball(FigureB).•Anon-rotatingspindletypemicrometerheadoronettedwithanantirotationdeviceonthespindle(FigureC)canbeusedifatwistingactionontheworkpiecemustbeavoided.•Ifamicrometerheadisusedasastop,thenaatfacebothonthespindleandthefaceitcontactsprovidesdurability.StemlocknuttypeFlatfaceSphericalfaceAnti-rotationdeviceFigureCFigureAFigureB■Non-RotatingSpindle•Anon-rotatingspindletypeheaddoesnotexertatwistingactiononaworkpiece,whichmaybeanimportantfactorinsomeapplications.■SpindleThreadPitch•Thestandardtypeheadhasa0.5mmpitch.•1mm-pitchtype:Quickertopositioning,etc.,thanthestandardtypeandavoidsthepossibilityofa0.5mmreadingerror.Excellentload-bearingcharacteristicsduetolargerscrewthread.•0.25mmor0.1mm-pitchtypeThistypeisthebestforne-feedorne-positioningapplications.3-65
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