coplanar profile of multiple surfaces

[greg2835]

Attached is how my company is calling out a coplanar profile of three surfaces that are not in-line with one another. I am still learning ASME Y14.5 and wanted to ask if this is an acceptable way of doing this or if better methods exist. I have seen profile used to callout coplanar surfaces when they are in-line using a centerline attached to the surfaces and a profile callout but not sure if that method could be adopted in the attached scenario.

Thank you in advance,

Greg

 

[powerhound]

The syntax may be off on this drawing but I don't think the callout is illegal because of it.

In the scenario you're talking about, it's a chain line, not a center line, that connects the surfaces.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[greg2835]

Thanks powerhound, that is encouraging since this method does not take up a lot of real estate on the drawing.

I would like to probe this thread a little bit further (meant to include this in the beginning) - attached now contains to continuous feature callouts on both FOS dimensions. Now, in total, does the drawing specify the following: "The three feet can vary in size from nominal ±.005 simultaneously (using a common gauge) and their relative flatness to one another is allowed to vary ±.0005." Hopefully that made sense :] Like I said, I'm still learning and having trouble finding examples when surfaces are not in-line with one another.

Best,

Greg

 

[CheckerHater]

To me second version looks more confusing as two dimensions appear to be attached to the same feature. Just an opinion.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[powerhound]

The CF symbol adds nothign to the drawing. With your original drawing, the pads had to all exist--be coplanar--within a .001 wide tolerance zone at the same time but that plane could tilt relative to the uninterrupted surface such that it could be .755 on one end and .745 at the other. Adding the CF symbol does not change that meaning.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[Belanger]

I wouldn't mess with the CF modifier. The GD&T on the first drawing was fine, but what needed clarification was that the three surfaces are supposed to be coplanar in the nominal state. That's what Powerhound was referring to -- you need some lines of continuation (chain lines) to show that the surfaces are designed to be at the same level.
The profile callout then states how much deviation is allowed between levels if they can't be perfectly coplanar.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[greg2835]

You're right, the CF does not add to the drawing (my mistake, hits forehead). Attached is another rev where I have moved the dimension in the bottom view over to the other foot (not sure why I had it on the other side). I have seen other engineers at my company simply place a 3X in the right view dimension and leave the bottom view void of feet height dimensions (attempting to encompass all three foot heights in one dimension). Are both of these methods valid?

Thanks,

Greg

 

[powerhound]

Just add a chain line to the lower view, attach your feature control frame to it with a leader line, and add 3X instead of "3 hatched surfaces." This will be compliant with Y14.5-2009. If you're working to the 1994 standard then replace 3X with "3 SURFACES".

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[CheckerHater]

Another possibility may be turning "hatched surfaces" into legitimate datum targets:

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greg2835]

Thank you gentlemen, I will attach one last version here for completeness. I forgot about datum targets (it has been awhile) but that would certainly work as well. Thanks CheckHater for uploading the image.

Best,

Greg

 

[pmarc]

I understand the main hero of this question is the profile callout, but in my opinion the .750+/-.005 dimensions deserve some attention and comments too.

 

[powerhound]

Okay pmarc, I'll bite.

Greg, if your intent is to also keep the three pads parallel to the bottom face within .001, then this will not do it.

Was that your intent from the start?


John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[greg2835]

For the example I provided controlling "how parallel" the bottom face is to the feet was not a requirement (however in reality the actual part I am detailing has other features that are controlled relative to the feet). However, if it was a requirement I would have added the callout [ profile | .001 | A ] and attached it to the bottom face. Other suggestions are most welcomed.

Greg

 

[powerhound]

Okay, just checking. Was that what was on your mind, pmarc?

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[powerhound]

One more thing, Greg.

There would be a different way to allow a larger deviation in size while still maintaining a tighter parallelism than what you suggested but since that wasn't your goal, I won't address it.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[pmarc]

Okay, just checking. Was that what was on your mind, pmarc?

I just meant that (at least to me) it is unclear what exactly is controlled by the .750 +/-.005 dimensions. If 3 pads are functional primary datum features, the most unambiguous way to control bottom face is to change the dimension to basic .750 and apply profile callout to control locaction of that face relative to the primary datum plane A. If additional orientation control is needed, parallelism tolerance wrt A should be applied as a refinement of profile tolerance.