>> P.533
MicrometersMicrometersø8Spindle30ʼø7.95ø6.35Spindleø6.3MeasuringFaceDetail30ʼCarbidetipCarbidetipNote:ThedrawingsaboveareforillustrationonlyandarenottoscaleMicrometerExpansionDuetoHoldingFramewiththeBareHandMeasuringrange300mm200mm100mm50mm246810152030Time(minutes)14131211109876543210Expansion(µm)toframeframewhenresult*Theabovegraphshowsmicrometerframeexpansionduetoheattransferthebarehandwhich,fromhandascanbeseen,maytotemperature-inducedexpansion.Whenmeasuringbyhand,caremustbetakenbecausethereferencepointwillchange(notethatthegraphvaluesarenotguaranteedvaluesbutexperimentalvalues).theinasignificantmeasurementerrordueisheldin31°C27°C21°C78910456Time(minutes)012320151050Expansion(µm)LengthStandardExpansionwithChangeofTemperature(for200mmBarInitiallyat20˚C)standard(astemperaturesweredifferenttimeaspeoplewhosehandshowshowaparticularmicrometerTheaboveexperimentalgraphexpandedwithshown)heldtheendofitataroomtemperatureof20°C.Thisgraphshowsthatitisimportantnottosetamicrometerwhiledirectlyholdingthemicrometerstandardbuttomakeadjustmentsonlywhilewearingglovesorlightlysupportingthelengthstandardbyitsheatinsulators.Whenperformingameasurement,notethatittakestimeuntiltheexpandedmicrometerstandardreturnstotheoriginallength.13-6HowtoReadtheScale■Micrometerwithstandardscale(graduation:0.01mm)(1)0545403530(2)(1)Outersleevereading(2)ThimblereadingMicrometerreading7.mm+0.37mm7.37mmNote:0.37mm(2)isreadatthepositionwherethesleevefiduciallineisalignedtothethimblegraduations.Thethimblescalecanbereaddirectlyto0.01mm,asshownabove,butmayalsobeestimatedto0.001mmwhenthelinesarenearlycoincidentbecausethelinethicknessis1/5ofthespacingbetweenthem.Approx.+1µmApprox.+2µmIndexlineThimblescaleIndexlineThimblescale■Micrometerwithvernierscale(graduation:0.001mm)Thevernierscaleprovidedabovethesleeveindexlineenablesdirectreadingstobemadetowithin0.001mm.3025201510(2)(1)Outersleevereading(2)Thimblereading(3)Readingfromthevernierscalemarking6.mm0.21mmandthimblegraduationline+0.003mm6.213mmMicrometerreading(1)0508642(3)0.01Vernierreading0.004mm(2)IndexlineThirddecimalplaceSeconddecimalplaceFirstdecimalplaceMillimetresTensofmm+Reading.004mm.09mm.9mm2.00.mmmm2.994mm(2)(1)Note:Indicatesfourdigits.50456420(1)0299mm(21and22inthiscase).0.003mm(3)isreadatthepositionwhereoneoftheverniergraduationsalignswithoneofthethimblegraduations.■Micrometerwithmechanical-digitdisplay(digitalstep:0.001mm)Thirddecimalplaceonvernierscale(0.001mmunits)Note:0.004mm(2)isreadatthepositionwhereaverniergraduationlinecorrespondswithoneofthethimblegraduationlines.MeasuringForceLimitingDeviceVarietiesRatchetstopAudibleinoperationOne-handedoperationRemarksFrictionthimble(Ftype)RatchetthimbleYesUnsuitableAudibleclickingoperationcausesmicro-shocksNoSuitableSmoothoperationwithoutshockorsoundYesSuitableAudibleoperationprovidesconfirmationofconstantmeasuringforceNote:0.21mm(2)isreadatthepositionwheretheindexlineisbetweentwograduations
| < 
| 
> | 
>>
