QC inspector - pre-qual job test question

[gabimo]

ASME Y14.5-2009.
Square block dimensioned with +\-. ( height/width/length). Perpendicularity of the side feartures relative to the bottom surface is limited by:
a.) title block tolerance (assuming one is available)
b.) rule #1
c.) answer a or b, whichever is greater
d.) answer a or b, whichever is smaller
e.) not defined ( more information needed).


Same question as above, but drawing implies ISO GPS with NO symbol E attached to the size dimension.

 

[SeasonLee]

JP nad pmarc

Thanks for your valuable comments, take a look on my latest version of the book, size dimension disappeared. So, which one is correct?

Season

 

[CheckerHater]

size dimension disappeared

And now it says "angularity" instead of "parallelism". I wonder if chart for "angularity" says "parallelism" (and has words "size dimension")

This is too much fun (or are we serious now?)

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[SeasonLee]

CH

No size dimension on angularity chart.

Season

 

[SeasonLee]

Well, we have lot of fun here and I know how to read the textbook now, will stop here and lets go back to the OP question.

Thanks all

Season

 

[Belanger]

Some time ago I came up with the part where Profile really does control all four parameters.

CH -- Certainly profile CAN control all four qualities. But when making a chart for a textbook I would never make a blanket statement that profile's primary job is to always control those four things. That was my only point.

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

 

[pmarc]

CH,
Yes, I meant part with directly toleranced size and general note parallelism. So if the general notes states "UNLESS OTHERWISE SPECIFIED, THE PARALLELISM IS 0.05" doesn't the +/-0.10 size tolerance together with default Rule #1 fall under UNLESS OTHERWISE SPECIFIED and override that general note?

J-P,
What can I say beside that I couldn't agree with you more.

 

[CheckerHater]

@pmarc:

I really don't see it that way. They must be satisfied together / simultaneously, so it must be less than 0.10 and less than 0.05 at the same time.

If they contradict each other, then, yes, size tolerance overrides general note. Do you have reference to support your point?

@pmarc & J-P:

Don't you guys think that the idea of "blanket statement" is to show ALL the possible situations?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

CH... so you are fine with the statement that angularity controls perpendicularity?
(I can show you an instance where that is true, but I wouldn't teach that as "blanket" statement about angularity in a textbook!)

My main issue was with the "P" and "I" in the chart given by SeasonLee. Why would one of profile's primary jobs be to control size?
And yet on the same chart, the runout symbols are parsed into P and I without similar logic.

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

 

[CheckerHater]

@J-P:

I totally agree that angularity controls perpendicularity. In fact, both parallelism and perpendicularity are just cases of angularity and can be abandoned and replaced by single control.

I always believed that primary function of profile is to control, well, a profile! Something like shape of a wing or turbine blade.
But the wing has a thickness and length of a chord, which are... sizes! So how you control wing without controlling size(s)?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

Profile at its heart is simply a form control. It MUST control form, and oh by the way sometimes it also controls size (if it wraps around a part, or if proper datums are given with basic dims). But we can't make a blanket statement that profile is a size control in itself.

You may recall that some websites promote using position on a single hole relative to only a perpendicular plane. Yet since that is only controlling perpendicularity, it is incorrect since it fails to fulfill position's primary function of location. Different topic, I realize, but it still speaks to the great misunderstandings out there regarding direct vs. indirect effects of certain GD&T symbols.


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

 

[mkcski]

Belanger:

I totally agree with your approach to profile and its fundamental control. When I teach, I state profile is used to control the shape (form) of non-standard shapes - those that are NOT flat, straight, circular or cylindrical - shapes that common machine tools produce. I then show them products that have non-standard shapes - auto bodies, aircraft fuselages, boat propellers, etc. and ask how do you control the form of these shapes. It gets the point across. I have an overhead projector and put my hand on the platen and let the shadow of my hand create a profile on the screen. I trace my hand with a marker and ask them to dimension it so someone can make a glove from a drawing. Eyes are wide open. We then get into 3D models to define non-standard shapes. I then add datums to show how they add orientation and then location by constraining motion.

 

[3DDave]

pmarc - each edge represents an angle between two faces. There can't be an edge without two faces. The number of alternatives grows significantly for anything but a simple block, but even for a simple block I've never seen an inspection report the bare minimum.

 

[pylfrm]

CheckerHater,

6 datum features and 5 angularity tolerances (one for each other face) referencing each datum feature gives a total of 30 tolerances (effectively 24 perpendicularity and 6 parallelism). I'm sure your example is more likely to actually show up in a title block though. I've seen similar requirements involving runout before.

I generally agree with your interpretation of "UNLESS OTHERWISE SPECIFIED". To count as otherwise specified, I think you'd need either a note that effectively states "the general tolerance does not apply here" or another tolerance of the exact same type, with identical modifiers and datum feature references if applicable, and a different tolerance value. In my experience this is a topic of much disagreement though. It seems even more problematic when CAD models get thrown into the mix.


3DDave,

TACOM probably has a good point. The tolerances never get checked, so remove them and dispense with the fantasy. Did they switch to a note such as "UNTOLERANCED DIMENSIONS ARE BASIC"?


pylfrm

 

[3DDave]

TACOM eliminated all titleblock tolerances, so no more .XX = +/-.03 for linear dimensions, et al. Since linear dimensions are obvious when there is no tolerance, those got fixed. Likewise explicit angles got fixed, but the assumed 90 degree angles that are frequently depended upon - Nope. Entire programs ignored that oversight. Since QA/QC only checks what's on the drawing and not what's missing - no pushback there either.

Making them basic would not help - almost no FCFs or datums.

 

[greenimi]

Oh my… I think poor inspector is really confused and he does not want the job anymore…………..

Now since the OP is still keeping silence (but, I guess nobody asked him/her anything, and honestly probably he/she is confused too on what is the “correct” answer) I will jump a bit into this discussion and try to get back to the main subject. I am doing this because I was the one to extend the original OP question from perpendicularity to parallelism (just for my own education)

Therefore, considering a title block defined like:
.X ±.05
.XX ±.01
.XXX ±.005
.XXXX ±.0015
ANGLES ±30 MINUTES

INTERPRET DIM. AND TOL. PER ASME Y14.5-2009/ ISO GPS --as applicable

What would be the “best answers” for the questions regarding the perpendicularity (OP question) and parallelism (my question –extended subject)


Do we agree that the answers would be:

Perpendicularity:
ASME-2009 a.)
ISO e.)

Parallelism:
ASME-2009 d.)
ISO e.)

Pmarc,
I probably agree that the OP question is poorly worded, but I guess we have seen very weak questions on the GDT books—different authors, GDTP preparation tests or even at the ASME exam itself, right? No excuse, for the OP, just a little bit of compassion/credit…And I know, that two wrongs does not make it right.

 

[CheckerHater]

@greenimi:

I would agree that perpendicularity answer for ASME will be "a." and parallelism answer "d." providing that envelope requirement is default and some sort of T/B tolerances is provided.

Now, as pmarc mentioned, given several different ways general tolerances may be specified in ISO/metric, the situation may require more careful consideration: what kind of tolerances are actually specified?

ISO Sub-case 1: Nothing is specified. The answer is "e." for both perpendicularity and parallelism.

ISO Sub-case 2: Envelope requerement is specified. The answer is "e." for perpendicularity, "d." for parallelism

ISO Sub-case 3: Drawing shows title block tolerance based on number of decimal digits like in your example. I personally dislike the idea, as leaving trailing zeros is forbidden in both ASME and ISO metric practices by default.
But I think it was Belanger, who argued that note actually qualifies as being "specified otherwise", so it may override default requirement. I still don't like it, but have to agree that he has a point.
So, if no other general tolerances are specified, the solution may be "a." for perpendicularity, "e." for parallelism.

ISO sub-case 4: separate document is referenced. We will use ISO 2768 as an example (sorry pmarc)

[li]First, you cannot simply "invoke" 2768, you have to reference it with proper parameters.[/li]
[li]ISO 2768 part 1 (linear dimensions) - perpendicularity controlled by general angle tolerance, parallelism not controlled.[/li]
[li]same with envelope requirement - parallelism will be controlled by envelope requirement. (answer "d.")[/li]
[li]ISO 2768 part 2 (geometric tolerances) - perpendicularity will be controlled by default perpendicularity, parallelism will be controlled by default parallelism[/li]
[li]same with envelope requirement - parallelism answer "d." - whichever is smaller[/li]
[li]ISO 2768 part 1 and 2 - default geometric tolerances will override dimensional tolerances[/li]
[li]Same with envelope requirement - parallelism answer is "d."[/li]

Are we having fun yet?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greenimi]

Thank you CH for the confirmation.

I already started to dislike ISO—and its lack of configuration management--, but that does not mean that I am in love with ASME (or at least not yet).

 

[CheckerHater]

Could you please elaborate, what exactly do you mean by "lack of configuration management in ISO"?

Maybe i will stop liking it too?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[greenimi]

You have to look through many different standards to came up with a complete definition of a concept.

 

[pmarc]

@pmarc:
I really don't see it that way. They must be satisfied together / simultaneously, so it must be less than 0.10 and less than 0.05 at the same time.
If they contradict each other, then, yes, size tolerance overrides general note. Do you have reference to support your point?

This is taken from the new draft of Y14.5, but I am more than sure that I saw this also in one of the other, already published, ASME Y14 series standards (I think it was Y14.41, but it would be great if someone could confirm):
"1.4.9 Unless Otherwise Specified (UOS)
The phrase "unless otherwise specified" or UOS is used to indicate a default requirement. The phrase is used when the default is a generally applied requirement and an exception may be provided by another document or requirement."

The way I see this definition in case of your scenario (and in general) is following. The parallelism 0.05 is the default requirement. Since the "thickness" dimension tolerance +/- 0.10 = 0.20 together with Rule #1 is capable of creating parallelism requirement for opposed faces, the exception to the default requirement has been created.

------------

pmarc - each edge represents an angle between two faces. There can't be an edge without two faces. The number of alternatives grows significantly for anything but a simple block, but even for a simple block I've never seen an inspection report the bare minimum.

I agree, there can't be an edge without two faces. I also agree that the number of alternatives grows significanlty for anything but a simple block. And that I have also never seen an inspection report the bare minimum.

But I do not agree that each edge represents an angle between two faces. An edge is just an intersection of two faces regardless of the angle between those two faces. The two faces can be perfectly perpendicular to each other, or be at any angle to each other, say 60 degrees, and the common edge will be exactly the same for both cases.

If we take 3 faces of a rectangular block into consideration (the bottom face, and two side vertical faces) that all have a common point (single corner), the situation is similar. All 3 edges generated by these surfaces can be perfectly perpendicular to each other, however the faces may not be at right angles.

I challenged your initial statement about 12 dimensions to check not because I wanted to point out that you were wrong, but because I wanted to show that the title block angular tolerances (which, unfortunately, are still very common in industry) are so vague that it is even not clear what to check. Do you agree?