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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