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Profile callout
2

Profile callout

Profile callout

(OP)
We have a callout on a customers drawing as follows;

Profile of .0005 to A.....There is a non basic dimension from A of .300

I see this as Parallelism to A, since the .300 is not basic. Am I correct with this definition.  

RE: Profile callout

Also, Is it multiple surfaces?
Frank

RE: Profile callout

dodge78,

   When I see a feature with multiple tolerances, I assume AND, not OR.  In this case, it must be within ±0.010", and and profile must be inside an envelope .0005".  The plus/minus tolerance is moot.

   If the customer wanted parallel, they would have specified parallel.

               JHG

RE: Profile callout

dodge78,
Though the callout seems at least suspect and most of folks would probably say is illegal or should be avoided, it is absolutely allowed per Y14.5. See fig. 6-18 in 1994 edition or fig. 8-27 in 2009 edition for similar profile of a line application.

And yes, you are correct - this callout controls parallelism of surface relative to A, plus the surface flatness.

P.S.: J-P are you there? I guess it is your hobby-horse.

RE: Profile callout

(OP)
Thanks..Pmarc, I agree and see these violations quite often.  

RE: Profile callout

No problem.
Small addition to my previous post. The profile callout you asked for controls 4 surfaces parallelism to A, their coplanarity, plus their flatness.

RE: Profile callout

I must disagree, the required basic dimension is "zero" and it is implied this is a coplainarity issue with an orientation requirement. It is clearly stated to be multiple surfaces on the drawing. The only problem, in my opinion, is the standard came too late to the party.
Frank

RE: Profile callout

(OP)
I agree...The A datum has its coplanarity callout of .00005 and side opposite A has the profile of .0005 to A, This I know would call the side opposite of A to be coplaner to itself of .0005, plus parallelism of .0005 to A. Since the .280 is not basic, I am not held to a bilateral location of +/-.00025

RE: Profile callout

I don't see a problem with this print at all. Datum A is comprised of 3 surfaces that are coplanar within a zone of .0005, then 4 surfaces are located with respect to datum A. Those surfaces must  be coplanar within .0005 of each other but the plane that they collectively make can be +/-.010 from datum A. The plane must also be basically oriented to A so it cannot skew from -.010 to +.010. Parallelism would not tie the 4 surfaces together as coplanar so it would not be appropriate to use here.

I really think this drawing is okay but I seem to be in the minority here.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Profile callout

Yes, it controls parallelism (and of course flatness) but the distance to A would fall back on the ± tolerance.   They chose to use profile because there are multiple surfaces.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: Profile callout

(OP)
I agree John, Just needed a second opinion. Thanks! Thanks everybody for your input!

RE: Profile callout

Gave pmarc a star for that one.  Of course, it would have been better to use a composite profile control, though I'm not sure how well it was understood in the '82 (or earlier) standard.  Assuming pre '94 because of the datum callout style.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: Profile callout

It was defiantly a logical extension of the principles. I had put together a company book that went into it around 1990 or so, just to try and cover this kind of thing. The management of the company proceeded to outlaw use of profile completely, it confused too many of the old checkers, "we didn't need this stuff in the good old days".
Frank
 

RE: Profile callout

I hear ya, Frank.  I saw one highly-regarded trainer's material, based on the '94 standard, which said that a composite profile was prohibited by the standard.  Had to argue my European colleagues out of that poorly founded belief.
Had expected a significant fight from other business units when I proposed the use of a general surface profile tolerance rather than ISO 2768, but was relieved/shocked when the proposal was recognized as a solution to many of the woes that some were experiencing.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: Profile callout

Jim,
Did they usally use a single value or a progressive scale for the profile general tolerance. With or without datum references? I have been working on the same thing for a long time and proposed in that my book I spoke of earlier.
Frank

RE: Profile callout

Jim:

I know that we have been around this bush many, many times but I would love to see how the DRF would apply correctly to all surfaces using the default profile of a surface application.

Could it be possible that the datum reference frame from the bottom of the part (datum A) would reflect the top relative to A|B|C when in reality it should only be referenced as A? Is that possible?

Dave D.
www.qmsi.ca

RE: Profile callout

Y14.5-2009: "In some cases, a single datum reference frame will suffice." Does that mean that one is required? Or would zero datum references with a composite profile tolerance here and there give the most tolerance, in some cases?

Peter Truitt
Minnesota

RE: Profile callout

Dave,
I really don't see the extra datum references as an issue it is a you are describing a complete framework, similar to what is required to measure parts on a CMM I believe the machine wants a complete reference framework (inspection guys?) set up first. If you end up not using all of them it is no real loss. This is the kind of compromises you get with general tolerancing, the standard itself, for many revisions (82, 94) has recommended a similar note for establishing dimensional controls in the past (section 4.4, NOTE).
Frank
 

RE: Profile callout

Frank:

I guess I am not a proponent of this approach since all features are treated equally while in real life, some features are vital to the part's function and mating relationship while others are irrelevant to its function. Jim and I have had discussions on this subject in the past and we, respectfully, stand diametrically opposed on this concept.

This approach also contravenes sections of the 2009 edition such as - 4.15    Functional Datum Features - "Only the required datum feature should be referenced in the feature control frame when specifying geometrical tolerances."

After many discussions here, I ended up developing a bit of a web page on this controversial subject.

 

Dave D.
www.qmsi.ca

RE: Profile callout

Dave,
Thanks, I would love to look at it. I believe I have seen some of those conversations and thank you also for pointing out 4.15.  I would tend to agree that they seem to be at odds. Like I said earlier general tolerancing does tend to blend all features together as if they are all equal, this is just as true for any titleblock tolerancing scheme so it is not new.
Frank
  

RE: Profile callout

If a Designer was opting to use default profile of a surface tolerance, it could be used for the "sluff off" dimensions utilizing a large tolerance with a note under the FCF stating "reference datums as applicable". This now meets the standard. The features that are vital to the part's function and relationship could be shown in separate FCFs with an appropriate tighter tolerance.

Dave D.
www.qmsi.ca

RE: Profile callout

Do adding or removing datum reference frames that are inconsequential to the function of the part affect the amount of tolerance available to the fabricator?

Peter Truitt
Minnesota

RE: Profile callout

Frank,
Each part would have its own general tolerance value, and drf.  This appeases the Y14.5 requirement that all features be controlled.  Beyond that, you override with local controls.  I.e. appropriate controls on your datum features, tighter or looser controls where needed/warranted on specific features.  Some of us who were more experienced would base our values on process knowledge and industry standard such as 2768, while others would pull a thumb-suck from 2768 without understanding the implications.  There were various philosophies about selecting which tolerance to put in the general tol frame too; ISO requires the loosest shop capability (or is it the tightest; I keep forgetting) while some designers emphasize the tightest with all looser tolerances being directly applied.  To me, it made sense to reduce detailing time by selecting the most common acceptable tolerance.  I found that most people then rationalized that they typically were too restrictive with their tolerances on most features anyway, and ended up accepting the general tol as adequate for even more features.

Yup, Dave, we agree to disagree.
Now, on 4-15, these are my thoughts; there is no HARM in adding the datum references even if they are not required for functionality PROVIDING THAT it does induce an additional setup for inspection.  I say this because if the DRF is not filled in, then you would need to break down the inspection setup to eliminate over-constraint; I pretty much guarantee that a CMM operator doesn't break down the datums for a new feature.  Taking a blend radius as an example, there's no value in the DRF - agreed - but are you going to break down the setup to verify it?  
Overall, nothing should be a carte-blanche for design or inspection, but some conveniences can save both parties significant time and effort ... and a general surface profile has proven to be one of them for many situations.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: Profile callout

Jim & Dave,
Thanks.

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