Atshuab ntxhua khaub ncaws, alsosometimesreferredtoasamachinebolt, isascrewthatistypicallydesignedtobe
fastenedtoanexisting, tappedholeonametalsurface, feem ntauinconjunctionwithacorrespondingnut.
Theobypesofscrewsarenotaslargeastheaveragescrew, feem ntau yog suavsivsaib chaw ua haujlwm
ofaninch (19.05mm) pob twheycanstillbelarger.Variationsbetweenmachinescrewsmainlyexistinoverall
qhov loj me, shapeofthehead, slottype, ntev, khoom, andcharacteristicsofthethread.
Amajorwayofcategorizingamachinescrewisbythetypeofslotinthehead, uaswilldeterminethekind
ofscrewdriverthatistodriveitintoitshole.Thetwomajorkindsofscrewdriversswithmachinescrews
isslottedandPhillipsheadscrewdrivers, butthereareseveralotherminortypesofscrewdriveholessuch
asTorx six-taw, lub hnub qub zoo li qubdiavholes thatrequiremorespecializedscrewdrivers.Specialized
homtsawgdawbholesmaybeimportantwhenitisdesiredthatthescrewsarenotinterferedwithfor
kev nyab xeeb kom zoo, txij li muaj kev pab tshwj xeeb los ntawm cov neeg tshwj xeebkhoom rau qhov tsis pom kev zoo.
vaj huam sib luag, rau khoom noj khoom haus, isagoodplaceforamachinescrewwithaspecializedtypeofhole.Othermachinescrew
headscanbesimilartoahexorsquareboltthathavenoscrewdriverslotandmustbeturnedwithawrench.
Theshapeoftheheadofamachinescrewwilldeterminehowitliesonceitisfastenedtoahole.Roundand
panheadswillprotrudefromaflatsurfaceoncetheyareattached.
thatareboredsotheylayflushwiththesurfacewhentheyhavebeenscrewedin.Theheadofasetmachine
ntsia hlau lojxeebhanthediameterntsuagtshuaj vam, sowhenitisattachitcanbedriventhroughahole
andadjustedtoadesireddepth.
Moreofthemajordifferencesbetweenmachinescrewsareinthecharacteristicsofthethread.Thispartof
ibqhonmachinescrewisoneofthemostimportant, becausethecorrespondingholesthattheyare
fastenedtowilltypicallybetappedtofitonlyonespecificsizeandtypeofscrewthread.Thesystemusedfor
ua cim tus kheejdifferentthreadsusuallyfollowsISO (InternationalOrganizationforStandardization) qauv,
qhovntawmtxojkevhlubtuamtsimcojcojkhoomqhovcojkevkhoompebkevpojntxoog
lub ntiaj teb.Twoofthemajorthreadcharacteristicsareitsdiameterandpitch, thev dhau losTsuas
betweenthreads.Thesescrewthreadscanalsobemadetobescrewedclockwise (xis-tuav) lossis
counter-clockwise (sab laug-sab laug).
Whilethesizeofamachinescrewisusuallyrelativelysmall, therecanstillbeavastamountofvariations
betweensize, shapeandlength, feem ntaudeterminedbytheirintendedpurposeandhowstrongtheyneedtobe.
Pringmetal tuaj yeem ua rau feem ntau ntawm cov tshuab screws asabove hais, kuj tseem ua haujlwm-madescrewscanalsobemanufacturedforspecificmachinesthatdonotevenhavetofollowany
ISOstandards.Tshuab ntxhoocanbemadeofanyofavarietyofmetalsorplastics.