Amachinescrew, Alsosometimesreferredtoasamachinebolt, isascrewthatistypicallydesignedtobe
fastenedtoanexisting, tappedholeonametalsurface, usuallyinconjunctionwithacorrespondingnut.
Thesetypesofscrewsarenotaslargeastheaveragescrew, usuallyranginginsizesuptothreequarters
ofaninch (19.05mm) buttheycanstillbelarger.Variationsbetweenmachinescrewsmainlyexistinoverall
dimensiune, shapeofthehead, slottype, lungime, material, andcharacteristicsofthethread.
Amajorwayofcategorizingamachinescrewisbythetypeofslotinthehead, whichwilldeterminethekind
ofscrewdriverthatistodriveitintoitshole.Thetwomajorkindsofscrewdriversusedwithmachinescrews
areslottedandPhillipsheadscrewdrivers, butthereareseveralotherminortypesofscrewdriveholessuch
asTorxsix colțuri, stele-shapeddriveholesthatrequiremorespecializedscrewdrivers.Specialized
tipuri de șuruburi cu șuruburi pot fi importante
safetyreasons, sinceitismoredifficulttoacquirespecializedtypesofscrewdrivers.Adangerouselectrical
panou, forinstance, isagoodplaceforamachinescrewwithaspecializedtypeofhole.Othermachinescrew
headscanbesimilartoahexorsquareboltthathavenoscrewdriverslotandmustbeturnedwithawrench.
Theshapeoftheheadofamachinescrewwilldeterminehowitliesonceitisfastenedtoahole.Roundand
panheadswillprotrudefromaflatsurfaceoncetheyareattached.Flat-headedscrewsaredesignedforholes
thatareboredsotheylayflushwiththesurfacewhentheyhavebeenscrewedin.Theheadofasetmachine
screwissmallerthanthediameterofthescrewthreads, sowhenitisattacheditcanbedriventhroughahole
andadjustedtoadesireddepth.
Moreofthemajordifferencesbetweenmachinescrewsareinthecharacteristicsofthethread.Thispartof
anygivenmachinescrewisoneofthemostimportant, becausethecorrespondingholesthattheyare
fastenedtowilltypicallybetappedtofitonlyonespecificsizeandtypeofscrewthread.Thesystemusedfor
Standardele characterizingdifferentthreadsusuallyfollowsISO (InternationalOrganizationforStandardization),
whichhavebeenestablishedtokeepconsistentdesignspecificationsinmachinepartsproducedthroughout
theworld.Twoofthemajorthreadcharacteristicsareitsdiameterandpitch, thelatterbeingthedistance
betweenthreads.Thesescrewthreadscanalsobemadetobescrewedclockwise (dreptaci) sau
antiorară (stângaci).
Whilethesizeofamachinescrewisusuallyrelativelysmall, therecanstillbeavastamountofvariations
betweensize, shapeandlength, mostlydeterminedbytheirintendedpurposeandhowstrongtheyneedtobe.
Pringmetal poate produce cele mai multe tipuri de șuruburi pentru mașini, mai sus menționate, de asemenea
ISOstandards.Machinescrewscanbemadeofanyofavarietyofmetalsorplastics.