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6Datums and DatumFeature References
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Define the difference between a theoreticallperfect dat!" and a dat!" feat!re.
#xplain how to create a dat!" reference fra"e
thro!$h reference% "ade on a drawin$.
tili'e all "ethod% for identifin$ dat!" feat!re%,
incl!din$ the !%e of tar$et point%, line%, and
area%.
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(a)e dat!" feat!re reference% in a feat!recontrol fra"e !%in$ the correct order of
precedence.
#xplain how a dat!" reference fra"e i%
e%tabli%hed fro" three referenced dat!"
%!rface%.
%e "aterial bo!ndar "odifier% on dat!"
feat!re reference% and be able to explain the%i$nificance of the "odifier%.
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Datum Reference Frame
(ade of three plane%
*lane% locate +, , axe%
*erfect fra"e
(ade fro" i"perfect dat!" feat!re%
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Degrees of Freedom
Three tran%lational
Three rotational
Tran%lational are alon$ +, ,
otational are !, /, w
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Datum Feature Symbol
Identifie% %!rface% and feat!re% of %i'e a% dat!"feat!re%
Tpicall one letter in a %0!are
Connected b %hort leader line to trian$le 1nl applied to ph%ical feat!re%
Dat!" tar$et %"bol identifie% dat!" tar$et%
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Flat Surfaces (Planes)
Co""onl !%ed a% dat!" feat!re%
#%tabli%he% dat!" plane
2i$h point% e%tabli%h dat!"
(a be %i"!lated with %!rface plate
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Cylindrical Features (Axes)
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Cylindrical Features
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Targets
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Target Points
3ocate and label each point
Di"en%ion% "a be ba%ic or toleranced
4 point% pri"ar, 5 point% %econdar, 6 point
tertiar
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Target Lines
3ocate and label each line
Di"en%ion% are tpicall ba%ic
7ide of dowel pin% are !%ed
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Target Areas
*hanto" line% for peri"eter
Contin!o!% line for %"all area%
3ocated b di"en%ion% or feat!re%
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aterial !oundary odifiers
(axi"!" "aterial condition 8((C9
(axi"!" "aterial bo!ndar 8((9
;o %"bol indicate% re$ardle%% of "aterial
bo!ndar 8(9
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"rder of Precedence
#%tabli%hed fro" order in feat!re control fra"e
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aterial !oundary odifierson Flat Datum Features
(a ha/e (, 3(, or ((
Generall, a/oid 3( and (( on flat %!rface%
;o 3( or (( on pri"ar dat!" feat!re
reference when feat!re i% flat 3( or (( on reference% to flat dat!"
feat!re% allowed onl when profile create% an
applicable bo!ndar
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aterial !oundary odifierson Datum Features of Si#e
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Least aterial
3ea%t "aterial condition 83(C9
3ea%t "aterial bo!ndar 83(9
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Com$ound Datum Features
otatin$ %haft i% tpical application
eflect% f!nctional need
Co"po!nd dat!" feat!re reference %how% two
dat!" letter% %eparated b a da%h (a al%o be !%ed to e%tabli%h a plane
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R! and ! on Surfaces
o!ndar farthe%t o!t%ide "aterial i% ((
o!ndar clo%e%t in%ide "aterial i% 3(
( i% a%%!"ed
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R!% !% and L! A$$licationto Datum Feature Surfaces
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