clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
(OP)
Hello,
I apologize in advance for English is my third language and I fear it is very difficult for me to translate my toughs on this one.
On figure 4-48 of asme y14.5 2009, looking at the 12.32-13.08 hole, there is a position box?? that says there is a .3 tolerance at LMC of the hole per primary datum A, secondary datum B and third Datum C.
I interpret it that my datum simulator for the holes axis must be parallel to the datum A. I then create a datum perpendicular to A passing though datum B. Datum C should then help orient my third datum simulator.
since the hole is a circle, hence has no feature that needs to be oriented in the C direction, why do they call it in the said box? couldn't they have omitted it? I don't get how the C in this case helps me inspect this hole.
thanks
Gerald
I apologize in advance for English is my third language and I fear it is very difficult for me to translate my toughs on this one.
On figure 4-48 of asme y14.5 2009, looking at the 12.32-13.08 hole, there is a position box?? that says there is a .3 tolerance at LMC of the hole per primary datum A, secondary datum B and third Datum C.
I interpret it that my datum simulator for the holes axis must be parallel to the datum A. I then create a datum perpendicular to A passing though datum B. Datum C should then help orient my third datum simulator.
since the hole is a circle, hence has no feature that needs to be oriented in the C direction, why do they call it in the said box? couldn't they have omitted it? I don't get how the C in this case helps me inspect this hole.
thanks
Gerald





RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
Gerald
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
I got a doubt in Fig 4-48 (Y14.5- 2009).
1) In FCF, Secondary datum is DATUM B. There are two DATUM B planes deriving from datum target lines. Then how DATUM B works ?
Regards
Vimal VV
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
Or it can be thought of as two planes -- but again it's really only one datum because of that 11.4 designed-in offset.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
PFA.
I am just making clear that whether my underatanding is correct. As per the conversation with you, the datum B can call out in the frame from two locations.because both are related by basic dimension.
In the fig, DATUM B is attached with the edge surface of pocket. And it is related with SURF X by basic dimension. In FCF i am calling DATUM B.
Based on my understanding i can dimension the hole from SURF X.Because SURF X is related with DATUM B. right ?
Regards
Vimal VV
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: clarification about ASME y14.5 2009 figure 4-48 position : is datum C futile?