if surface profile tol in the title block ok? 7

[juanMElvl300]

Hi users hope you are all doing good.

I have two simple questions.

1) is it ok to have a profile surface tolerance in a drawing title block? (see the below picture)
2) if so, with it apply to all surfaces for inspection?

I'm used to seeing the old way; this profile tolerance must be new. (to me btw)

something like this was the old tol. block
X.X = ±0.25
X.XX = ±0.12
X.XXX = ±0.06
X.XXXX = SEE DIM TOLERANCE

 

[Belanger]

The old method you mentioned (using ±) may seem easier, but it had many problems such as not controlling location adequately (datums were unknown or had no precedence indicated). So yes, that general profile method is OK, and usually actually better.
With that profile of a surface callout of 0.3, imagine the entire part (yes, all surfaces) to be contained within a tolerance "shell" of 0.3 mm. Not only does that control sizes, but it controls the relationship between features.
However, any other tolerances on the field of the drawing would override the general profile. That's where the designer has to be careful; there may need to be datum features identified and related to each other, and other relationships established.

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

 

[greenimi]

J-P,
I will strongly disagree with you.
If a feature is defined with a plus - minus dimension then the profile within 0.3 is NOT applicable.
UOS note of profile within 0.3 is relevant only for the features with no control.

This statement I find it incorrect.
"""""""""With that profile of a surface callout of 0.3, imagine the entire part (yes, all surfaces) to be contained within a tolerance "shell" of 0.3 mm. Not only does that control sizes, but it controls the relationship between feature""""""""

 

[greenimi]

And one more comment

J-P Belanger's statement
"However, any other tolerances on the field of the drawing would override the general profile. That's where the designer has to be careful; there may need to be datum features........."
is questionable at best.

In order to avoid all the issues presented above DO NOT use "Unless otherwise specified". You are asking for trouble.
Just delete UOS.

 

[3DDave]

For many castings an overall profile of a surface tolerance is appropriate with the possibility that some areas are better controlled and have some smaller tolerance applied to them. Since it is formed as a single operation a casting can be considered a single feature for such a control. It's not universally used but the application has an interpretation that isn't ambiguous.

 

[TheTick]

Blanket profile tolerances are common in my field. Usually they reside in drawing notes.

Wherever you place it, be sure it can be tailored by the designer/drafter and controlled within the drawing (not automatically updated if title block changes). Also true for the rest of TB tolerances. Internal control of values and datums. I've seen title block updates that change blanket tolerances and cause thousands of dollars of out-of-spec waste.

 

[3DDave]

Yeah - watch for CAD systems that are set to use "Latest" for formats. Also watch out for people who do drawing update checks and look only at exactly what was on the change order.

 

[Belanger]

If a feature is defined with a plus - minus dimension then the profile within 0.3 is NOT applicable.

Yes, that's why I explicitly wrote that "any other tolerances on the field of the drawing would override the general profile" (emphasis added).
Sorry if my follow-up statement seemed questionable to you -- I was hinting at some other profile callout in one of the views that would override this general one; then datums would probably be needed, which may mean that datums get referenced in this general profile of 0.3 -- I was trying to avoid a big, confusing explanation for the OP.

This statement I find it incorrect: "With that profile of a surface callout of 0.3, imagine the entire part (yes, all surfaces) to be contained within a tolerance "shell" of 0.3 mm. Not only does that control sizes, but it controls the relationship between features."

I presume you are familiar with an "all over" profile callout -- this is the same thing. All bases are covered: size, location, orientation, and form (SLOF). So you'll have to expand on what you disagree with.

In order to avoid all the issues presented above DO NOT use "Unless otherwise specified". You are asking for trouble.

Now it's my turn to disagree. Are you saying that the profile of 0.3 must always be THE only tolerance for every feature on that part? Or are you assuming that every reader just knows that anything in a general tolerance block can be overridden? Either one of those sounds mighty dangerous.

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

 

[Burunduk]

With that profile of a surface callout of 0.3, imagine the entire part (yes, all surfaces) to be contained within a tolerance "shell" of 0.3 mm.

I have to disagree with you this time.
This would be a valid interpretation if the profile control was applied with an all over symbol, or if it was constrained by datum references invoking a simultaneous requirement. Alternatively, it would also apply if the number of surfaces was specified. But not as currently shown in the note image posted above.

 

[Burunduk]

juanMElvl300,
A general UOS profile note is widely acceptable, and it is a good practice to replace the "traditional" tolerance block by it, from the reasons mentioned by Belanger. But usually it is specified with the functionally appropriate datum references. This way, size of width features, as well as orientation and location of all features that are not otherwise specified, are controlled.
As it is now, it only controls the form of all individual features which are not otherwise specified.

 

[greenimi]

I presume you are familiar with an "all over" profile callout -- this is the same thing. All bases are covered: size, location, orientation, and form (SLOF)

Yes, I am. Fig 11-21/2018 shows it.
However, that figures does not have any plus-minus dimennsions and tolerances. If the drawing has any plus-minus dimensions then UOS note breaks everyhting apart and it is subject to multiple legal interpretations.

Are you saying that the profile of 0.3 must always be THE only tolerance for every feature on that part? Or are you assuming that every reader just knows that anything in a general tolerance block can be overridden? Either one of those sounds mighty dangerous.

I agree here with you. And that is all BECAUSE of the ambiguous definition of UOS.
I would not recomend to use UOS eitherway, unless a note (however lenghty) is added to clarify if UOS is/ could be used as refinement or a nullification of the original/ specified requirement.

 

[3DDave]

If I have a note: "UNLESS OTHERWISE SPECIFIED PAINT PER XYZ" on a part, is that ambiguous? I could mark an area "OMIT PAINT" or "PLATE PER ZYX." Is it unclear what "otherwise" means? Perhaps a paragraph or multiple paragraphs defining all the "otherwises" possible to ensure that every possible test that might come up is covered? Would that be sufficient?

It's possible this needs a novelization treatment.

The largest problem is that notes like that are largely ignored. For example - most of the drawings I've seen include some default angle tolerance. This applies to every pair of surfaces/features that appear to be at right angles as well as those pairs with explicit angle dimensions. Over 30 years not once has any inspection report I've come across (in 6-7 different company's work) enumerated all the surface/feature pairs covered by the 90 degree rule and listed the part variation.

So ignored in fact that one program, for no reason, had the customer demand that no titleblock tolerances, including angle tolerances, be used. This left all nominally perpendicular surface/feature pairs with no tolerance limits at all. QA never said a word.

So, it seems clear to me that the only ambiguity is when someone says - hey this is controlled by something does that mean it is otherwise specified?

Lewis Carroll, with a strong interest in language and logic covered this:

"When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean- neither more nor less." "The question is," said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty, "which is to be master-that's all."

 

[Belanger]

Burunduk and Greenimi,
Let's go back to the OP's graphic. He was kind enough to highlight in blue that this profile callout applies to "all surfaces." Thus, it's equivalent to an FCF on the field of the drawing with leaders pointing to every surface.
You (Burunduk) stated that this has a different meaning than specifying the number of surfaces or using the words "all over" (or the symbol for all over) -- please elaborate on the difference.

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

 

[greenimi]

Let's go back to the OP's graphic. He was kind enough to highlight in blue that this profile callout applies to "all surfaces." Thus, it's equivalent to an FCF on the field of the drawing with leaders pointing to every surface.

If any feature is defined with plus-minus--a feature of size for example- (just to give you an example) then the profile within 0.3 is NOT applicable.
If you have an angular relationship (angle dimension) between two features then, again, the profile within 0.3 is NOT applicable.
If, for example - you have ONLY a parallelism tolerance specified then the profile within 0.3 is NOT applicable

Why, all the above?
Because something else IT is specified, and then unless otherwise specified = UOS is nulified.

 

[Belanger]

I think I get your point, greenimi -- since profile encompasses form, location, orientation, size, then a parallelism tolerance would tackle the orientation and form, but it would be unclear if the location and size aspects fall back to the general profile or simply be undefined. That might be good fodder for further discussion.

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

 

[greenimi]

J-P,

And one more comment (and this has been discussed before)
Let's say in fig 6-30/2018 you DON'T have profile|0.1|A| (center upper area of the figure) for the face of the vertical feature. Again, only parallelism within 0.06 at A is shown.
Assuming the above, are you saying that UOS ALL SURF within 0.5A|B| is applicable?
If you said , YES (it is applicable), I would argue NO, (it is not applicable) because it is already specified otherwise (with orientation control, parallelism) and the drawing is incomplete.
Why your (YES) interpretation is better than mine (NO) interpretation?
Could you say that for sure or become opinion based statement?

 

[greenimi]

J-P,
I think we posted in the same time

 

[3DDave]

It is as applicable as the amount of control that remains to it. With that UOS profile of a surface control the drawing cannot be incomplete.

 

[juanMElvl300]

To everyone, thank you so much. Your answers were excellent.

Typically, I have seen surface profile tolerance for surfaces that mate parts to match characters.
I have never seen it used for a complete drawing before and especially for small CNC parts with no surfacing or matching surfaces.

once again, thank you so much

 

[chez311]

As it is now, it only controls the form of all individual features which are not otherwise specified.

I would have to disagree. In Y14.5-2018 a profile tolerance applied in a tolerance block or general note is a perfectly valid way to specify an All-Over specification per para 11.3.1.5(c). I saw this was likely missed in the other thread discussed recently too.

11.3.1.5 All Over Specification. A profile tolerance may be applied all over the three-dimensional profile of a part UOS. It shall be applied in one of the following ways:
(a) place the “all over” symbol on the leader from the feature control frame as shown in Figure 11-10
(b) place the term “ALL OVER” beneath the feature control frame
(c) place the profile tolerance requirement in the general tolerance block or general notes