All about screws关于螺丝

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1、Allaboutscrews:"Howlargeofascrew/boltdoIneed?""Whattypesofscrewsareoutthereandwhatarethefor?""Whatarewashersfor,anddolock-washerswork?""Howtightshouldascrewbe,andhowdoesthataffecthowmuchloaditcanhandle?""Coarsevs.Finethread?"ContentsCommontypesofwood,machineanddryw

2、allscrewsandtheirusesCommonmachinesscrews,headtypesandusesThreadtypes:UNC,UNRF,M,...what'savailableandwhenshoulditbeused?Sizing:howbigascrewisneededforagivenload?Howdoestightnessaffectthis?Installation:Howmuchtorqueandwhy?ScrewGrades:What'sthedifferencebetweengrades

3、andwhenshouldIusethem?WashersandLocknuts:WhentousewhichkindMaterialSelection:steel,stainless,zincplated,galvanized...AdditionalResourcesandReferencesTerminologyandbasicidentificationWhat'sthedifferencebetweenaboltandascrew?Mostsources(liketheMachinery'sHandbook)define

4、screwsandboltsintermsofhowtheyareinstalled:ifyouturntheheadit'sascrew,ifyouturnanutit'sabolt.Ahexheadcapscrewandhexboltmaylookidentical.Thisguidereferstobothinterchangeably.Wood,SheetMetalandDrywallScrews-differences,uses,andheadtypesWoodScrews:Thesehaveacoarserpitch(fe

5、wthreadsperinch)thansheetmetalormachinescrews,andoftenhaveanunthreadedshank.Thethreadlessshankallowsthetoppieceofwoodtobepulledflushagainsttheunderpiecewithoutgettingcaughtonthethreads.Somewoodscrewsaretaperedfromtiptohead,also.Thissitelistspre-drillsizesforvarioussizeds

6、crews.SheetMetalScrews:Usuallythreadedallthewaytotheirhead,thesewillworkinwood,butwoodscrewsshouldn'tbeusedinmetal(thisisbasedonhardwarestoreemployeeadvice,notexperimentalevidence).Mostofthesescrewsareself-tappinginthattheyonlyrequireapre-drilledhole(pre-drillsizes),but

7、somecomewithself-drilling(showninabovepic)orself-tappingtips.Here'salargelistofdifferenttypesoftips,themorecommononesappeartobeA,AB(pointed)andB(nopoint).Here'sagoodguidetothedifferentpointtypesanduses.Seemorepicsofthreadcuttingscrewshere.Evenmoregoodpicturesofdifferenth

8、eadtypes.DrywallScrews:Thecoarsethreadversionismeanttosecuredrywalltowoodwhilethefinethreadversionisfo