Profile Callout Bilateral 2

[Ksplice]

Hi,

I have a question on profile tolerances called out bilaterally. please see attached sketch. the profile callout is pointing to a line that is 0.10 inside the actual profile. my interpretation of this is that the tolerance zone is established centered on the 0.10 offset. is this correct or does the zone start at the 0.10 and is not centered on it. Also if someone could point me to the page in the ASME 2009 standard where this is addressed i would most appreciate it as i have been unable to find it.

thanks,

 

[pmarc]

Ksplice,
You should look to paras. 8.3.1.2 & 8.3.1.3 plus fig. 8-4 of Y14.5-2009 ("alternate practice"). Although the figure shows profile of surface application, it can be applied to profile of a line tolerance too.

That being said, the picture you attached is not in accordance with the standard, so it is really hard to correctly interpret the intent of profile of a line callout shown.

 

[SeasonLee]

This is not a standard compliant sketch, few comments on this figure:

1. For a bilateral unequal distribution tolerance, a phantom line and a basic dimension will be used to specify the offset of the tolerance zone, .010 is the offset basic dimension but where is the phantom line?

2. Any profile control is applied to the true profile, the leader line of the FCF cannot indicate to the offset phantom line (actually it’s not a phantom line on the sketch).

3. It’s a composite profile tolerance callout on the sketch, per Y14.5 2009 standard composite profile tolerance can only be applied to patterns of surfaces, however there isn’t any extended symbol to include additional surfaces (between symbol, all around, all over,… etc.), the sketch FCF only directed to a line segment, so I don’t think line profile can be used on the composite profile control.

Season

 

[pmarc]

... per Y14.5 2009 standard composite profile tolerance can only be applied to patterns of surfaces

Could you indicate where exactly the standard says so?
Imagine a simple rectangular block with bottom surface being assigned as datum feature A and top surface located by basic height dimension (for example 10) from datum A. Let's say I want to control location of the top surface to A by profile of surface callout within equally bilateral 0.5, but also tighten orientation of the surface to A within equal bilateral 0.1. Am I not allowed to use composite profile FCF when controlling this single feature:
|0.5|A|
|0.1|A|?

 

[SeasonLee]

pmarc

An interesting things you will notice when you made a comparison on the standard of 94 and 09, you can’t find out any words of PLTZF and FRTZF in 94 standard on the composite profile section (see page 172), but you can easily find out these two terms in 09 standard when they explain the composite profile tolerance (see page 168). As you know PLTZF is short for Pattern-Locating Tolerance Zone Framework, that’s why I mentioned “composite profile tolerance can only be applied to patterns of surfaces”, I can’t find out where exactly the standard says so, but I can provide what Alex said on his latest textbook, please ref to the attached for details.

For your example, you may use multiple single-segment profile tolerance FCF to control it.

Season

 

[CheckerHater]

Per 2009 composite profile is used in 2 different ways:
1. Composite profile tolerancing of a feature (see Para. 8.6.1.1)
2. Composite profile tolerancing of a pattern (see Para. 8.6.1.2)
Maybe not the best idea, but it’s right there in black and white.

 

[pmarc]

SeasonLee,
That is interesting - I mean the statement in Alex's book. I already e-mailed to him for clarification, so hopefully I will get a feedback soon.

In my example multiple single segment profile FCFs would not work. Keep in mind that in this case, the second FCF would also control location of the top surface to A, and I do not want to do that. Besided this would be in conflict with the first FCF, as they both would control exactly the same things with different tolerance values only. That is illogical.

There is, however, a workaround. I should simply switch the lower segment of composite profile FCF into parallelism callout. That would result in the same geometrical requirements.

But...What if the top surface in my example was not nominally flat, but for instance an arc or sine-like (see attachment)? Would it really be in conflict with Y14.5-2009 to go with composite profile FCF in such case? Would there be any alternative way if I wanted to control orientation of the top surface to A tighter than location to A?

http://files.engineering.com/getfil...-89e7-ccea1a167ae1&file=composite_profile.png

 

[pmarc]

I am answering to my last question:
I could go with customized datum reference frame in the second single segment profile FCF to free translation of contour relative to A, but still, does it mean that composite profile FCF could not be applied?

 

[Belanger]

I would say that composite can certainly be applied, pmarc. Even if both parts of the composite FCF reference datum A only, as shown in your sketch, we are to understand that the 0.5 controls location (distance to A) and the 0.2 controls orientation to A (and form, of course).

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

http://www.gdtseminars.com

 

[SeasonLee]

pmarc

The exercise (circle D/E) from Alex’s book is almost same as your post, the top radius is controlled by multiple single segment profile FCF.

I have a conclusion after reading the book (but I am not quite sure it’s correct or not): The top radius is only a single feature, it’s not a pattern of surface, only multiple single segment profile FCF can control it. On the contrary, the slot (right side view) is a pattern of surface since there is an around symbol, so composite profile FCF will take care.

Season

 

[Belanger]

SeasonLee, check out Fig. 8-20 of the standard. That uses a composite FCF and it's not a pattern.

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

http://www.gdtseminars.com

 

[pmarc]

SeasonLee,
For me it is obvious that if Alex assumed that applying composite profile FCF to a single surface was illegal, the excercise you just posted simply could not show otherwise. If it did, this would be like denial of the statement you marked in yellow in previous post.

Let's wait for his answer. This may not happen today or even tomorrow, but I think it is worth to wait. OK?

J-P,
I think that in the light of definition of pattern [1.3.42], and I believe this is what SeasonLee is sticking to, fig. 8-20 may be considered as having composite profile FCF applied to a pattern. There is however another question: why hasn't the all around been mentioned in this definition?

 

[SeasonLee]

J-P
There is an around symbol on the callout, the irregular opening groups 4 corner radii and 4 sides, so it’s a pattern for sure.

Season

 

[Belanger]

I think that in the light of definition of pattern [1.3.42], and I believe this is what SeasonLee is sticking to, fig. 8-20 may be considered as having composite profile FCF applied to a pattern.

Interesting... I guess to me that raises two additional questions:
1 - Why does the caption of Fig. 8-20 call that rectangle a "feature" in the singular sense?
2 - If I have a plate with a single slot in it (sort of like Fig. 7-34 but with one, not three) then the very strict definition SeasonLee is taking would hold that to be a pattern (two straight edges and two arcs). Would that be appropriate for a composite FCF (position and/or profile)?

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

http://www.gdtseminars.com

 

[SeasonLee]

Here is the pattern definition form Alex’s book, it will be very interesting for all of us (I was refreshed when I read it first time)

Season

 

[Belanger]

This is a wild ride! By the definition just given by SeasonLee, Fig. 8-20 is not a pattern. I'm hoping that vindicates my post from 12:54 today.

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

http://www.gdtseminars.com

 

[pmarc]

SeasonLee,
To be honest the definition of pattern is not that important here. Please read carefully paragraphs 8.6 and 8.6.1. Word "pattern" and abbreviations "PLTZF" or "FRTZF" are not there. So why to focus on pattern at all?

 

[SeasonLee]

Well, it raised from the hi-lighted statement from Alex book, I think it’s worth to wait for his feedback.

Season

 

[SeasonLee]

Let’s go back to the OP, what makes me interested is the composite profile callout, can we use profile of line on the composite profile FCF callout?

Season

 

[pmarc]

I would shortly answer - no, we should not.