huangyhg

profile of a surface for dimensional tolerance
good morning.
i am working with a customer drawing (see attached pdf)and i am not sure of the way they are using this feature to control tolerance. in this example they claim that the entire part is held to the profile of a surface tolerance, which would be in this case ±2.5mm. i have a few issue's with this but because i deal with this so little i am not sure.
to use this feature wouldnt all of the dimensions have to be basic?
is this a valid way to measure a distance feature from a datum? practical?
does the tolerance block imply ± 2.5, or a range of 5, say if nominal was 30 would a range of 29 to 33.5 be ok.
are there any flaw's with this control?
i did forget to mention that the next line under the feature control frame states that dimensions w/o tolerance are reference.
seems like a typo to me. all of those untoleranced dimensions are reference? are these features defined elsewhere with tolerances?
believe it if you need it or leave it if you dare.fff"> - robert hunter
yes, i think they should all be basic and i don't think there are enough.
racefanjtd,
"unless otherwise specified..."
maybe it is not a standards compliant drawing. i think the intent is pretty clear.
jhg
you are correct that all dimensions shown on the drawing should be basic but, frankly, i really dislike this way of applying gd&t.
gd&t should apply on features where there is a function and relationship within the part or to the mating part. i don't think that this applies here but it easy for the design to apply.
a 5 mm profile means a +/- 2.5 mm from the basic dimension or theoretical dimension.
dave d.
looks like typical drawing information for the automotive industry. you've gotta remember that it's only surface tolerance that they've given you. any holes or fastener locations would have a different location tolerance.
also, you haven't supplied us with the complete drawing so i can't commit to a total comment but typically the dimensions shown would be basic and should be stated as such in the title block.
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