Amachinescrew, Alsosometimesreferredtoasamachinebolt, isascrewthatistypicallydesignedtobe
fastenedtoanexisting, tappedholeonametalsurface, usuallyinconjunctionwithacorrespondingnut.
Thesetypesofscrewsarenotaslargeastheaveragescrew, usuallyranginginsizesuptothreequarters
ofaninch (19,05 mm) buttheycanstillbelarger.Variationsbetweenmachinescrewsmainlyexistinoverall
veľkosť, shapeofthehead, slottype, dĺžka, materiál, andcharacteristicsofthethread.
Amajorwayofcategorizingamachinescrewisbythetypeofslotinthehead, whichwilldeterminethekind
ofscrewdriverthatistodriveitintoitshole.Thetwomajorkindsofscrewdriversusedwithmachinescrews
areslottedandPhillipsheadscrewdrivers, butthereareseveralotherminortypesofscrewdriveholessuch
asTorxsix špicaté, hviezda-shapeddriveholesthatrequiremorespecializedscrewdrivers.Specialized
typy skrutiek, ktoré môžu byť dôležité, keď sú potrebné, aby boli posádkyzasiahnuté
safetyreasons, sinceitismoredifficulttoacquirespecializedtypesofscrewdrivers.Adangerouselectrical
panel, forinstance, isagoodplaceforamachinescrewwithaspecializedtypeofhole.Othermachinescrew
headscanbesimilartoahexorsquareboltthathavenoscrewdriverslotandmustbeturnedwithawrench.
Theshapeoftheheadofamachinescrewwilldeterminehowitliesonceitisfastenedtoahole.Roundand
panheadswillprotrudefromaflatsurfaceoncetheyareattached.Flat-headedscrewsaredesignedforholes
thatareboredsotheylayflushwiththesurfacewhentheyhavebeenscrewedin.Theheadofasetmachine
screwissmallerthanthediameterofthescrewthreads, sowhenitisattacheditcanbedriventhroughahole
andadjustedtoadesireddepth.
Moreofthemajordifferencesbetweenmachinescrewsareinthecharacteristicsofthethread.Thispartof
anygivenmachinescrewisoneofthemostimportant, becausethecorrespondingholesthattheyare
fastenedtowilltypicallybetappedtofitonlyonespecificsizeandtypeofscrewthread.Thesystemusedfor
Normy characterizingdifferentthreadsusuallyfollowsISO (InternationalOrganizationforStandardization)
whichhavebeenestablishedtokeepconsistentdesignspecificationsinmachinepartsproducedthroughout
theworld.Twoofthemajorthreadcharacteristicsareitsdiameterandpitch, thelatterbeingthedistance
betweenthreads.Thesescrewthreadscanalsobemadetobescrewedclockwise (pre pravákov), alebo
proti smeru hodinových ručičiek (ľavák).
Whilethesizeofamachinescrewisusuallyrelativelysmall, therecanstillbeavastamountofvariations
betweensize, shapeandlength, mostlydeterminedbytheirintendedpurposeandhowstrongtheyneedtobe.
Pringmetal môže vyrobiť väčšinu druhov strojných skrutiek, ako už bolo spomenuté, tiež zákazkové skrutky môžu byť vyrábané pre špecifický stroj, ktorý je určený na výrobu nových skrutiek.
ISOstandards.Machinescrewscanbemadeofanyofavarietyofmetalsorplastics.