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■Constant-forceDevice•Amicrometerheadttedwithaconstant-forcedevice(ratchetorfrictionthimble)isrecommendedformeasurementapplications.•Ifusingamicrometerheadasastop,orwheresavingspaceisapriority,aheadwithoutaratchetisprobablythebestchoice.■SpindleLock•Ifamicrometerheadisusedasastop,itisdesirabletouseaheadttedwithaspindlelocksothatthesettingwillnotchangeevenunderrepeatedshockloading.■MeasuringRange•Whenchoosingameasuringrangeforamicrometerhead,allowanadequatemargininconsiderationoftheexpectedmeasuringrange.Sixmeasuringranges,5mmto50mm,areavailableforstandardmicrometerheads.•Eveniftheexpectedmeasuringrangeissmall,suchas2mmto3mm,itwillbecosteffectivetochoosea25mm-strokemodelaslongasthereisenoughspaceforinstallation.•Ifalongmeasuringrangeofover50mmisrequired,theconcurrentuseofagaugeblockcanextendtheeffectivemeasuringrange.(FigureD)•Inthisguide,therange(orstrokeend)ofthethimbleisindicatedbyadashedline.Forstrokeends,considerthethimbleasmovingtothepositionindicatedbythelinewhendesigningthejig.■Ultra-fineFeedApplications•Dedicatedmicrometerheadsareavailableformanipulatorapplications,etc.,whichrequireultra-nefeedoradjustmentofspindle.■ThimbleDiameter•Thediameterofathimblegreatlyaffectsitsusabilityandthe"fineness"ofpositioning.Asmall-diameterthimbleallowsquickpositioningwhereasalarge-diameterthimbleallowsnepositioningandeasyreadingofthegraduations.Somemodelscombinetheadvantagesofbothfeaturesbymountingacoarse-feedthimble(speeder)onthelarge-diameterthimble.■GraduationStyles•Careisneededwhentakingareadingfromamechanicalmicrometerhead,especiallyiftheuserisunfamiliarwiththemodel.•The"normalgraduation"style,identicaltothatofanoutsidemicrometer,isthestandard.Forthisstyle,thereadingincreasesasthespindleretractsintothebody.•Onthecontrary,inthe“reversegraduation”style,thereadingincreasesasthespindleadvancesoutofthebody.•The"bidirectionalgraduation"styleisintendedtofacilitatemeasurementineitherdirectionbyusingblacknumeralsfornormal,andrednumeralsforreverseoperation.•Micrometerheadswithamechanicalorelectronicdigitaldisplay,whichallowdirectreadingofameasurementvalue,arealsoavailable.Thesetypesarefreefrommisreadingerrors.Afurtheradvantageisthattheelectronicdigitaldisplaytypecanenablecomputer-basedstorageandstatisticalprocessingofmeasurementdata.Micrometerheadwithconstant-forcedeviceMicrometerheadwithoutconstant-forcedevice(noratchet)FigureDGaugeblockHead’smeasuringrangeObtainedmeasuringrange05504525204505NormalgraduationstyleReversegraduationstyle052520208010900090108020Bidirectionalgraduationstyle3-66
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