Profile callout 2

[dodge78]

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.

 

[KENAT]

What is the orientation of A to the profile &/or .300 dim?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[fsincox]

Also, Is it multiple surfaces?
Frank

 

[dodge78]

See attachement...In this case its the .280 which is +/- .010

 

[drawoh]

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

 

[pmarc]

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.

 

[dodge78]

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

 

[pmarc]

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.

 

[fsincox]

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

 

[dodge78]

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

 

[powerhound]

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

 

[Belanger]

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

 

[dodge78]

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

 

[MechNorth]

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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fsincox]

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

 

[MechNorth]

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

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fsincox]

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

 

[dingy2]

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.

http://www.qmsi.ca

 

[ptruitt]

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

 

[fsincox]

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