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preventinterferenceattheexternalMJthreadroot(justastheUNJexternalthreadprofilerequirestheUNJinternalthread).However,MexternalthreadsarecompatiblewithMandMJinternalthreads(justasUNandUNRexternalthreadsarecompatiblewithUNandUNJinternalthreads).
e. ISOmetricfastenermaterialstrengthpropertyclasses(grades)
.AsgiveninISO898-1,ISOmetricfastenermaterialpropertyclasses(grades)shouldbeused.Forexample,fastenermaterialISOpropertyclass5.8meansnominal(minimum)tensileultimatestrength500MPaandnominal(minimum)tensileyieldstrength0.8timestensileultimatestrengthor0.8(500)=400MPa.(Inafewcases,theactualtensileultimatestrengthmaybe
approximately20MPahigherthannominaltensileultimatestrengthindicatedviathenominalpropertyclasscode.ConsultTable10,below,forexactvalues.)Manyanchorbolts(L,J,andUbolts,andthreadedrod)aremadefromlowcarbonsteelgrades,suchasISOclasses4.6,4.8,and5.8.
f. Preferreddiameters
.Preferrednominaldiametersforboltsandthreadedrodareaslistedbelow.Thefourthserieslistedbelowshouldbelimitedtounusualrequirementswhennoneoftheprecedingseriescanbeused.Referenceindividualstandardspriortospecification.SizesM5toM45arecommonlyusedinconstruction.
g.
Boltversusscrewdefinition.Thecorrectdefinitionofboltandscrewisasfollows.Boltsareheadedfastenershavingexternalthreadsthatmeetanexacting,uniformboltthreadspecification(suchasM,MJ,UN,UNR,andUNJ)suchthattheycanacceptanontaperednut.Screwsareheaded,externally-threadedfastenersthatdonotmeettheabovedefinitionofbolts.Forfulldiscussionofmisdefinitionsandcorrespondingconfusionregardingthesetwowords,seedetails.
h.
Handyconversionfactors.Imperialconversionfactors,verifiedaccuratetothedecimalplacesshownviamultiple,independent,crediblesources,are25.4mm/inch(exact),4.4482216152605N/lbf,6.89475729318MPa/ksi,47.880259Pa/psf,112.98483(Nmm)/(inlbf),157.08746(N/m^3)/pcf,16.0184634(kg/m^3)/(lbm/ft^3),27679.9047(kg/m^3)/(lbm/in^3),9.80665(m/s^2)/gravity(exact).Roundingtheseconversionfactorstoafewlessdecimalplaces,wehave4.448222N/lbf,6.89476MPa/ksi,47.8803Pa/psf,113.0(Nmm)/(inlbf),157.087(N/m^3)/pcf,16.01846(kg/m^3)/(lbm/ft^3),27679.9(kg/m^3)/(lbm/in^3).
i.
Metricsystem(SI).TheabbreviationforthemetricsystemisSI,theInternationalSystemofUnits(fromtheFrench,SystemeInternationald'Unites).ItevolvedfromtheoriginalFrenchmetricsystemandiscurrentlybeingusedvirtuallyworldwide.Longthelanguageuniversallyusedinscienceandamongtechnicallyadeptindividuals,SIhasalsobecomethedominantlanguageofinternationalcommerceandtrade.AllnewUSAstandards(ASTM,ANSI,SAE,IEEE,ASME,etc.)arenowwritteninmetric,astheleadengineersintheseorganizationsrecognizetheimportanceoftryingtogettheUSAontrackwithtechnicallyadvancedcountries,inanefforttoregainlostUSAcompetitivenessinaglobaleconomy,asthereisessentiallynoglobalmarketforthearchaic,oddball,incompatibleproductdimensionsUSAarbitrarilycomesupwith,whiletheyforfeitindustriesandjobstothird-worldcountrieswhohavenoproblemunderstandingsomethingsosimpleandfulfillingtheneedefficiently.IEEEwasintelligentenoughtorecognizethisdecadesago.Japanalsowasintelligentenoughtorecognizesimplematterssuchasthislongago.Thissmallcountry,defeatedinWWIIonly60yearsago,hassincecapturedalargeportionoftheglobaleconomyduetotheirintelligentprogress,andconsequentlyhas
becomeamajorglobalfinancier,whileUSAhasbecomeaworld-classdebtortothetuneoftrillionsduetoinefficientbusinesspractices,loweducationallevel,slackerism,andinabilitytosolveorunderstandevensimpleproblemssuchasmetricconversion.
8.FastenerData.Tables9and10providemuchofthedataavailablefordifferentmetricfasteners.Table9comesverbatimfromRef.1,includingwhatappeartobeafewtypos,marked"[sic],"below.Table10,ontheotherhand,hasbeenverifiedaccurateperISO898-1andASTMF568M.
Firstchoice: M22.5345681012162024303642Secondchoice:
M3.514182227333945Thirdchoice: M15172540Avoid: M79112628323538
Table9FASTENERDATA
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