【转帖】hello all. i have been seeing this

yang686526

hello all. i have been seeing this
hello all.
i have been seeing this type of callout on many customer drawings lately.  the customer is a large company with a reputation for high standards of quality.  i know what i think of this type of callout, but need a sanity check.  please share your thoughts...  thanks!
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i wouldn't know what to make the feature to. profile to itself? maybe the drafter fell asleep? zzzzz
chris
solidworks 07 4.0/pdmworks 07
autocad 06
it appears that the drafter is trying to use the profile tol'd surface as the z datum.  i don't use profile a lot, but i would be willing to venture that it is not allowed to use the geo tol'd surface as its own datum for profiling since the question of how to reference it as a locational or orientational surface when it is the subject of being located or oriented by the very same geo tol.  i am very interested to seeing other answers to your question.
matt
cad engineer/ecn analyst
silicon valley, ca
there are over 10 examples in y14.5 with combined feature control frame and datum feature symbol.  i initially thought that this example shown was incorrect, until i flipped through the standard and came across an example with runout.  look at fig. 6-52 in asme y14.5.  i would say that it could be a legal calout, but i would be very sure that i had a conversation with the person responsible for making the print and asked what they were attempting to do.  it is not very clear.
marcelino vigil
gdtp t-0377
unfortunately, you are correct about the standard. it is something that does defy logic and hope the next version does not reference a datum unless you have one.
dave d.
marcelino - there is a big difference between runout and profile....it's apples and oranges.  it appears to me to be a mistake.
heckler   
sr. mechanical engineer
swx 2007 sp 4.0 & pro/e 2001
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this post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.
thanks, guys.
is this allowed for any other control other than runout?  i will be trying to find examples in the standard this afternoon.  i guess i'm going to have to get my head around this concept of a datum relative to itself...
we have already talked with the customer regarding this, and they agreed that there may be a better way to define the part.  i do want to be on solid ground though with any suggestions we submit to them.
thanks again!
i agree with heckler.  6-52 is not an example that could be used as an example of profile.  runnout is a completely different animal.  in runnout, you can reference the a feature's center line as a datum while still controlling that feature's surface.  it is allowable, but not very clear, since technically, datum d has two different meanings at that point.
i cannot think of an example where this could apply in a profile.  i would love to see the actual usage of this geo tol.  
matt
cad engineer/ecn analyst
silicon valley, ca
i don鈥檛 see anything technically wrong with the profile callout, surface z must still have acceptable form and orientation relative to the drf |x|y| to be in compliance. if  z is  datum target area then there boundaries, defined with basic dimensions from the drf |x|y|z|, that define and limit where that profile requirement resides. unlike putting a flatness callout on a continuous primary datum surface where the boundary extends to the edge of the surface 鈥?no matter what its edge variability is 鈥?datum target areas require definition for their boundaries and there is nothing wrong with using the fully constrained drf to constrain that boundary. for that matter x1, x2, x3  or y1, y2 could be similarly controlled for their co-planarity,  offset planarity, and/or orientations with boundaries by a similar callout.
also i agree with fcsuper that, 鈥測ou can reference the a feature's center line as a datum while still controlling that feature's surface.  it is allowable, but not very clear, since technically, datum d has two different meanings at that point.鈥?/i>
paul
in our situation, z is being used for radial and for planar surfaces (depending on the drawing).  the radii are relatively large compared to the part size, so it will not be inspected for runout.