FORDWORLDWIDEFASTENERSTANDARD
Date:1996-10-01
WD900
GeneralSpecificationsforSpacedThreadTappingScrews
1.SCOPE.
Thisstandardspecifiesthegeneralanddimensionalrequirementsforspacedthreadtappingscrewswith
variousheadforms.
2.REFERENCES.
ISO1478-TappingScrewsThread
WD950-MaterialandPerformancerequirementsforCarbonSteelTappingScrews
3.GENERALREQUIREMENTS.
3.1DIMENSIONSANDTOLERANCES.
ThedimensionsandtolerancesofPanHead,RoundWasherHead,RaisedCountersunkHead,Flat
CountersunkHead,HexagonHeadandFlangedHexagonHeadSpacedThreadTappingscrews
mustbeinaccordancewithTables1thru6,Figures1thru5includedinClauses2thru7,and
AppendicesA,BandCasappropriate.
3.2SCREWTHREADS.
3.2.1THREADLENGTH.
FortypesABandBscrewsofnominallengthsequalto8diameteror38mm,whicheveris
shorter,thefullformthreadsshallextendclosetotheheadsuchthatthespecifiedminor
diameterlimitsaremaintainedtowithinonepitchmaximumfromtheundersideofhead.
Screwsoflongernominallengthsshallhaveaminimumlengthoffullformthreadequal
to6diametersor38mm,whicheverisshorter.
3.2.2SCREWLENGTH.
Thelengthofthescrewshallbemeasuredparalleltotheaxisofthescrewfromthelargest
diameterofthebearingsurfaceoftheheadtotheextremepoint.Thetoleranceonlength
shallbeasspecifiedinTable