Fastener Design Manual - NASA

1 NASA' ,:.?.,'-''-"'".'-*'"_,'"'" '" '",;L, ,OhioERRATA NASA Reference Publication 1228 Fastener Design Manual Richard T. Barrett March 1990 The Manual describes various platings that may be used for corrosion control including cadmium and zinc plating. It does not mention outgassing problems caused by the relatively high vapor pressure of these metals. The Fastener Manual was intended primarily for aeronautical applica-tions, where outgassing is typically not a concern. Issued June 17, 2008 >AppendixesA ,platings,lubricants,corrosion,lockingme thods,washers,inserts,threadtypesandclas ses,fatigueloading, ,loadsonafastenergroup,combiningsimultan eousshearandtensionloads,pulloutloadfort appedholes,griplength,headstyles, ,nuts, ,requiringcarefulconsiderationoftemperat ure,corrosion,vibration,fatigue,initialp reload, ,finishes,torques, ,washers,lockingmethods,inserts,rivets, ,butmostboltsaremadeofcarbonsteel,alloys teel, , , , (CRES) :(1)Theboltplatingmaterialisusuallytheli mitingfactoronmaximumservicetemperature.

2 (2)Carbonsteelandalloysteelareunsatisfac tory(becomebrittle)attemperaturesbelow 65 F.(3)Hydrogenembrittlementisaproblemwith mostcommonmethodsofplating,unlessspecial proceduresareused.(Thissubjectiscoveredm orefullyinthecorrosionsection.)(4)Series 400 CRES containsonly12percentchromiumandthuswill corrodeinsomeenvironments.(5)Thecontacto fdissimilarmaterialscancreategalvaniccor rosion,whichcanbecomeamajorproblem.(Galv aniccorrosioniscoveredinasubsequentsecti onofthismanual.) , , ,exceedingthesafeoperatingtemperatureoft heplatingcancauseprematurefastenerfailur eduetohydrogenembrittlementaswellaslosso fcorrosionprotection.(Asummaryofplatings andcoatingsisgivenintableII.) ,cadmium-platedpartsmustbebakedat375 Ffor23hours,within2hoursafierplating, F,itsusefulservicetemperaturelimitis450 F,TABLEI.

3 SUMMARYOFFASTENERMATERIALSM aterialCarbonsteelAlloysteelsA-286stainl ess17-4 PHstainless17-7 PHstainless300seriesstainless410,416,and 430stainlessU-212stainlessInconel718stai nlessInconelX-750stainlessWaspalloystain lessTitaniumZincPlatingSurfacetreatmentZ incplateCadmiumplate,nickelplate,zincpla te,orchromiumplatePassivatedperMIL-S-500 2 NonePassivatedFurnaceoxidizedPassivatedC leanedandpassivatedperMIL-S-5002 PassivatedperQQ-P-35orcadmiumplatedNoneN oneNoneUsefuldesigntemperaturelimit, F 65to250 , , , Fbuthasausefulservicetemperaturelimitof2 500F.(Itscorrosion-inhibitingqualitiesde gradeabove140 F.)PhosphateCoatingsSteelorironisphospha tecoatedbytreatingthematerialsurfacewith adilutedsolutionofphosphoricacid, ,ksi55andupupto300upto220upto220upto2207 0to140 Upto180185upto220 Upto180150upto160 CommentsSomecankusedat900 F--------- Oxidationreducesgalling47ksiat1200 F;willcorrodeslightly140ksiat1200 F136ksiat1200 F----- -----zinc,iron, ,ortheycanbedippedinoilorwaxtoimprovethe ircorrosionresistance, F(forheavyzinc)to400 F(forironphosphate).

4 NickelPlatingNickelplating,withorwithout acopperstrike(thinplating), F, SUMMARYOFPLATINGSANDCOATINGST ypeofcoatingCadmiumZincPhosphates:Mangan eseZincIronChromiumSilverBlackoxide(ando il)Preoxidation(CRES)fastenersonlyNickel SermaGardandSermatelWStalgardDiffusednic kel-cadmiumUsefuldesigntemperaturelimit, F.(4)Itcanalsobeusedforcoatingtitaniuman daluminums.(5) :(1)Becausetheprocessmustbedoneinaspecia llydesignedvacuumchamber,itisquiteexpens ive.(2) , ,itisacceptableformaximumoperatingtemper aturesof800to1200 , F.(SPST echnologieshastestedSermatelW-coatedfast enersat900 Fwithoutdegradation.)Thiscoatingprocessp reventsbothhydrogenembrittlementandstres scorrosion, offtheshelf withSermatelWorSermaGardcoating, ,inorganic-organiccoatings, , , (perAMS2416).Thepartisthenbakedfor1houra t645 , ,Inc.

5 ,Limerick, , ,Rockford, , F, , ,thenormal drytorque ( ). ,combinedwithanoilfilm, , ,greaseorwax,graphite, , ,theyarelimitedtoanoperatingtemperaturen otmuchgreaterthan250 F.(Abovethistemperaturetheoilorgreasewil lmeltorboiloff.)Inaddition, , ;cannotbeusedinvacuumCannotbeusedinvacuu mCanbeusedinvacuumCanbeusedinvacuumBecau seoilboilsoff,mustbeappliedaftereachhigh -temperatureapplicationDonotuseonaluminu mormagnesiumparts;extremelyexpensive Removablefastener compoundsonlyaCarrierbo,lofftemperature, GraphiteL Dry (usuallyoilorwater) , , ,themaximumoperatingtemperaturegiveninth eirsalesliteratureis500 ,Ventura, ~ti~Emhart,Broadview, F, ,buttiecompoundleavesnongallingoxidesofn ickel,copper, , F, (suchasLoctite) ,theyareepoxies,whichhaveamaximumoperati ngtemperatureofapproximately275 , (anode)ofthetwomaterialsiserodedanddepos itedontheleastactive(cathode).

6 Notethatthefartheraparttwomaterialsarein thefollowinglist, :(1)Magnesium(mostactive)(2)Magnesiumall oys(3)Zinc(4)Aluminum5056(5)Aluminum5052 (6)Aluminum1100(7)Cadmium(8)Aluminum2024 (9)Aluminum7075(10)Mildsteel(11)Castiron (12)Ni-Resist(13)Type410stainless(active )(14)Type304stainless(active)(15)Type316 stainless(active)(16)Lead(17)Tin(18)Munt zMetal(19)Nickel(active)CswagelokCompany ,Solon,ohio.(20)(21)(22)(23)(24)(25)(26) (27)(28)(29)(30)(31)(32)(33)(34)(35)(36) Inconel(active)YellowbrassAdmiraltybrass AluminumbrassRedbrassCopperSiliconbronze 70-30 Copper-nickelNickel(passive)Inconel(pass ive)TitaniumMonelType304stainless(passiv e)Type316stainless(passive)SilverGraphit eGold(leastactive) , , , , (usuallypitsorcracks) ,thehighertheheat-treatingtemper-atureof thematerial(andtielowertheductility), , (220-ksiA286fastenersareavailableonspeci alorder).

7 Thehigherstrengthstainlesssteelfasteners (180to220ksi)areusuallymadeof17-7 PHor17-4PH, (suchasH-11toolsteelwithanultimatetensil estrengthof300ksi) ,itispreferabletousemorefastenersoftheor dinaryvarietyandstrength,ifpossible, (greaterthan180ksi)bringonproblemssuchas brittleness,criticalflaws,forgedheads,co ldrollingofthreads, ,dyepenetrant,magneticparticle,threadrad ius, , :(1)Hydrogenchemicalreaction:Hydrogenrea ctswiththecarboninsteeltoformmethanegas, ,niobium, ,theyreducetheoverallstrengthofthepart.( 2)Internalhydrogenembrittlement:Hydrogen canremaininsolutioninterstitially(betwee nlatticesinthegrainstructure) (3) ,thisconditionwouldnotbepresent,Mostplat ingspecificationsnowstatethataplatedcarb onsteelfastener shallbebakedfornotlessthan23hoursat375+2 5 Fwithin2hoursafterplatingtoprovidehydrog enembrittlementrelief (perMIL-N 25027D).

8 Inthepasttheplatingspecificationsrequire dbakingat375&25 ,andmostplatingspecificationswererevised in1981 ( ), ,hydrogenembrittlementfailureofcadmium-p latedpartscanstartaslowas325 F, , , ,whichcauseslooseningundervibration, ,Theboltcanhaveastandardthread, ,withthecommonprinciplebeingtobind(orwed ge) Thesplit-beamlocknut( )hasslotsinthetop, beam segmentsaredeflectedoutwardbythebolt, ,heavy-dutyhexFigure2, Split-beamlocknut7 DistributedbyDetroitTap&ToolCompany,Detr oit,Michigan, i:;: +e ip ica ( )isacommonlocknut, :(1)Thenutcanbeformedinoneoperation.(2)T hetemperaturerangeislimitedonlybythepare ntmetal,itsplating,orboth.(3) TheNylok8pellet(ofnylon) , , Thecastellatednutnormallyhassixslotsassh owninfigure6(a). (dependingontheuser ssNylokFastenerCorporation,Rochester,Mic higan.)

9 ~Ny[okpellet*If~NutFigure4. Nylokpelletlocknut.~Collar/Figure5. Lockingcollar,~Cotter(a)(b)(a)Slots.(b) ) (b). Thesenutsarenormally jammed togetherasshowninfigure7,althoughthe experts , , ,iftheouternutistightenedmorethantheinne rnut, ,ajamnutcanbeusedonaturnbuckle, , (a)Figure8. DurIocknut,Serrated-facenut(orbolthead). -Theserratedfaceofthisnut( ) ,theirserrated-facebolts(Durlock180) AlthoughIockwiringisalaboriousmethodofpr eventingboltornutrotation,itisstillusedi ncriticalapplications,particularlyinthea erospacefield,Thenutsusuallyhavedrilledc orners, (a),andatypicalnutlockwiringassemblyissh owninfigure9(b).Easystart(b)(a)Multiplef astenerapplication(double-twistmethod,si nglehole).(b)Castellatednutsonundrilleds tuds(double-twistmethod),Figure9. ,ratherthanonboltsandnuts, Thetaperedthreadisavariationofthedirecti nterferingthread, Anutplate( ).]

10 ]on,tneycannaveLockingactionstartsTotals ealandlockingactionFigure10, Taperedthread,(a)(b)(a)Fixed.(b) , (orepoxies) , ,Loctite242isforremovablefasteners, ,NDIndustries,Nylock,3M, ribbon , , F;theworstoneswillfunctionatonly200 ( ) , ,unlesstheyhaveserrationsontheirsurfaces , , ,Newington, ( (a)and(c))orincreasethespringconstant( (b)). ,buttheyarealsoavailableinaluminum,silic on,brome,phosphor-bronze,stainlesssteel, , , , (a)Smooth.(b) TypesofBelIevilIewashers.(a)(b)(c)(a)Ins eries.(b)Inparallel.(c) (orStar)LockwashersToothIockwashers(fig, 15) (ornut) , ,inmatingparts,orboth, (a)(b)(a)Flat,(b) ToothIockwashers.~8 maximummisalignmentofnutandbearingsudace atassemblyFigure16. ,molded, ,wear-resistanttappedholeinasofimaterial suchasplasticandnonferrousmaterials, (nominally1 )gives,forexample,a10-32boltinanequivale nt5/16 ,therearetwotypesofinserts:thosethataret hreadedexternally,andthosethatarelockedb ysomemethodotherthanthreads(knurls,serra tions,grooves,orinterferencefit).