Paralell vs Profile....

[Tenkan]

I have a flat part with 3 raised surfaces on one side that are shown coplanar. The customer wants those three surfaces to be parallel to datum A, an opposite surface, within 0.3mm. While waiting for an answer, everything about the design looks like something sits on the 3 pads....

What I want to do on my drawing is use a profile callout with a 3 surfaces note but my team is rejecting that in favor of parallel because its easier to inspect and not a callout of the customer. My question is if I was to place a 3 surfaces note attached to the FCF of a parallel callout would that mean the 3 surfaces are parallel to A collectively?


lightweight, cheap, strong... pick 2

 

[pmarc]

That would mean the surfaces would have to be parallel to A within 0.3, but not collectively. That is, mutual locational relationship between the surfaces would not be controlled. Profile of surface would define this interrelationship.

 

[CheckerHater]

I think we are missing something here.
Is there a toleranced dimension between “opposite surface” and 3 raised surfaces?

 

[Belanger]

Profile of a surface would probably be the easier one to inspect. And it's probably what the customer wants; they just used the wrong terminology (as pmarc says, the pads could be parallel to one another but still be offset from each other).

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

 

[pmarc]

Regardless of whether the dimension is directly toleranced or basic, the parallelism callout will not control locational relationship between the surfaces.

 

[CheckerHater]

Isn't what customer want count as "functional requirement"?

Where does it say, that customer wants to control locational relationship with parallelism?

Will profile without basic dimension control location?

Aren't we making up way to many things?

Questions, questions...

 

[pmarc]

I do not feel like making up anything (although Koda94's additional clarification would certainly help).

Will profile without basic dimension control location? It will not control location of surfaces relative to datum(s), but it will control locational relationship between the surfaces without focusing on their location relative to the datum(s).

 

[fsincox]

Your alternate "PC" option is use:
"COMMON ZONE" or "CONTIUOUS FEATURE" under the parallel callout these are standard terminologies that will most likely be understood to convey your intended message.
Frank

 

[CheckerHater]

I guess the question was

My question is if I was to place a 3 surfaces note attached to the FCF of a parallel callout would that mean the 3 surfaces are parallel to A collectively?

If customer insists on parallelism rock solid, Continuous Feature will require to treat features geometrically as one AKA collectively (Para. 2.7.5).
Combined with that Tangent will require to pick highest points of all 3.
Not as much fun as profile, but may do the job.

 

[CheckerHater]

Frank, you beat me :-(

 

[fsincox]

I was always told a note can still be used to suppliment drawing intent. While I prefer the profile method, myself, I am well aware of people who hate profile. I once worked in a place where the chief engineer outlawed it because it upset his checkers too much.
That's how I can relate to CH's name
Frank

 

[Tenkan]

the position (height) of the 3 surfaces is dimensioned from the top surface of the plate whereas datum A is the bottom surface and the plate thickness is its own dimension. good question though.

Your alternate "PC" option is use:
"COMMON ZONE" or "CONTIUOUS FEATURE" under the parallel callout these are standard terminologies that will most likely be understood to convey your intended message.
Frank

this sounds like the solution if they wont allow me to use a profile callout. It sounds like the same intent as if I used "2 SURFACES" except I've never had to address this with a parallel spec and thought it only allowed used with Datum or Profile multiple surfaces.

Profile of a surface would probably be the easier one to inspect. And it's probably what the customer wants; they just used the wrong terminology

agree. I have a hard time explaining how profile would be easier to inspect in some cases (especially vs. position) so I always get my drawings marked up to replace profile callouts in those situations. I see customer drawing errors all the time but the problem is most of my team doesnt want to "change" a callout even if it defines the design intent accurately. (I design part drawings for welded assemblies the customer designs, I only get the final assembly drawing to work with) The argument is that I am adding callouts the customer did not want or require.......

lightweight, cheap, strong... pick 2

 

[fsincox]

I have to do this kind of PC cr*p all of the time, I assume others do too? It is bad enough we have to work with out of date standards and out of date thinking. Then the standards committee come along and cannonize it (CF) and people start to complain that there are too many different options.
(see current threads)
Frank

 

[Tenkan]

I have to do this kind of PC cr*p all of the time, I assume others do too?

LOL Frank most days are fine but some days my drawings are so micromanaged I wonder why they require drafters initials on the drawings at all. There is something about questioning a callout that makes people feel their GDT knowledge is being undermined and then their attitude flairs up. To me it’s not about being right it’s about finding the right answer.

lightweight, cheap, strong... pick 2