Trick questions 1

[3DDave]

Per the 2009 version:

Is a titleblock tolerance a direct tolerance?
Are there any indirect tolerances?

 

[pmarc]

Q1: Would the dimension in red be considered directly or indirectly toleranced for its maximum limit?

Q2: Would Rule #1 apply to this dimension?

 

[greenimi]

pmarc,

First of all Welcome Back,

Q2: I would say No, 5 MIN is not subject to the rule#1.
Q1: Here I would say, indirectly, but I know I might be wrong. (Maybe the answer it is an opinion based answer with no specific guidance from the standard). Therefore, since I came here to leran, I care less is I am correct or otherwise.

 

[3DDave]

It cannot be, per the standard, "indirect" as that term is not defined. Since the tolerance which the designer feels can allow a functioning part (MIN) is applied directly to the value it is, like all tolerances in '2009+ versions, by definition direct.

 

[CheckerHater]

According to Standard, "limit tolerances" are direct tolerances, so MIN limit is direct tolerance.

According to the same Standard, "Geometric Tolerances Directly Applied to Features" are direct tolerances. Profile tolerances are applied to features, so MAX limit, defined by Profile tolerances is direct tolerance.

According to the same Standard, basic dimensions are not directly toleranced, DIM 5 MIN is NOT basic, so here goes your last chance.

And NO, Rule 1 does not apply.

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

 

[pmarc]

greenimi,

I agree with your assessment. The dimension in question is not subject to Rule #1 because there is no directly toleranced maximum size limit for the dimension.

To 3DDave's point, is explicit definition for indirectly toleranced dimension in the 2009 standard needed? It wouldn't harm to have it, but this does not automatically mean that every dimension is directly toleranced per the standard, in my opinion.

In Y14.5-2018 they added definition for directly toleranced dimension (para. 3.27), which will hopefully make the determination easier for those who follow or will follow the 2018.

 

[3DDave]

In 2009, all tolerances are under the "Direct Tolerancing Methods" paragraph, including geometric characteristic tolerances. There are no exceptions.

 

[CheckerHater]

@ pmarc & 3DDave:

FYI: Direct tolerancing methods paragraph happily made it into Y14.5-2018:

Geometric tolerances are still direct, no matter what Para. 3.27 says (I will keep my fingers crossed until next Standard release ).

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

 

[3DDave]

I see that they converted Direct Tolerancing Methods to be solely for features of size, though in the same breath they both define limit dimensioning as directly applied and contrast directly applied tolerance values with limit dimensions and then don't have an example of non-geometric direct tolerancing, but instead add Plus and Minus Tolerancing as a new category. Sigh.

I think too many cooks have been spoiling this broth for far too long.

 

[pmarc]

The 5 MIN dimension is not directly toleranced for its MAX value because the MAX value is calculated from nominal thickness and two profile tolerances (which, by the way, are direct tolerances applied to each side of the wall).

 

[3DDave]

Hmm - don't see where it needs both ends to have a set tolerance to qualify but, again, the tolerance there is directly applied.

 

[pmarc]

You were looking for an example of an indirect tolerance. I gave you one, which you apparently don't agree with. That's OK.

 

[3DDave]

The problem isn't one of conversational English language usage - the problem is within the confines a standard which doesn't recognize anything but "direct" as a tolerance application method. There's no example in the standard using the term "indirect tolerance" while referring to an example application.

That example might run afoul of the general prohibition against double dimensioning, so it's not the greatest basis, and it might also run afoul of unbounded variation which is not specifically prohibited.

 

[pmarc]

There is also no example in the standard explaining that a single radius of arc length less than 180 degress is not a feature of size. Does it mean that all such radii are features of size?

I don't see any double dimensioning in my example. The 5 MIN dimension is just an additional requirement that needs to be met together with the two profiles. And most of all, it does not conflict with the two profiles. See attached example taken from Y14.8-2009 "Castings, Forgings, and Molded Parts".

https://files.engineering.com/getfile.aspx?folder=1cb2ec68-bccb-4865-adc0-67ada48bc869&file=3-24.JPG

If this example is not double dimensioning, then definitely mine is not either. (By the way, unlike my example, the figure from Y14.8 shows the wall thickness directly toleranced for its both size limits).

Also, the wall thickness in my example has a maximum limit defined by the two profile tolerances, therefore I am not sure why its variation is considered unbounded.

 

[3DDave]

I see, per ASME Y14.5-2009, 1.4(a) that "MIN" is not a tolerance at all as "minimum" and "maximum" preclude using a tolerance.

Very tricky.

ASME Y14.5-2009, 1.4(a) also conflicts with the idea that basic dimensions have no tolerance.

 

[mfgenggear]

I am not as good as some, but in order to have any definition of a terminology, there has to be clear and concise written definition, otherwise we are going upstream with out a paddle.
even all the experts will disagree or agree.
for example ref dimensions could be indirect tolerancing.
for a engineering drawing to be clear and concise it must be dimensioned as to cover all geometrical requirements. thus direct tolerancing.
indirect tolerancing could be an aid to the manufacturer, I would say U.O.S dimensions could be determined both ways. but who knows
as long as the manufacture and the customer are on the same understanding. If to make it clearer I will add notes to clarify any dimensioning.

 

[powerhound]

It has always been my understanding the "indirect" tolerancing was referring to a geometric tolerance on a feature, not on a dimension. So while the dimension is not directly toleranced it is still used in determining whether a feature is in tolerance.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[3DDave]

Powerhound, that might have been true until they specifically included geometric tolerances as direct tolerances. Mind you, it's not the colloquial interpretation of what an "indirect" tolerance might be, but the way the ASME Y14.5 standard has defined all tolerances as being direct and defined no tolerances as being indirect that is the reason it's a trick question.

What would it mean to have geometric tolerances not directly applied to features? For sure it was important to write that sentence in ASME Y14.5-2009, 2.2(c) exactly that way, but then to offer no alternative plan for how to explain just how directly applied a tolerance needs to be?

There's a clear distinction between a datum, a datum feature, a datum feature symbol, a datum feature simulator (theoretical), a datum feature simulator (physical), and a simulated datum.

There is no such distinction for any tolerance alternative to a directly applied tolerance, at least not starting with '2009.

(edit: Missed one)

 

[powerhound]

So I guess we have tolerances directly applied to dimensions and directly applied to features. The geometric tolerance on a feature is an indirect tolerance of the associated basic dimension. Maybe that's what it's supposed to mean.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[Burunduk]

Is a titleblock tolerance a direct tolerance?
Are there any indirect tolerances?

Dimensions to which titleblock tolerances apply are directly toleranced dimensions.

Dimensions can be directly or indirectly toleranced (basic).

Tolerances are just the specified allowed variation.
How did you came across the idea of an "indirect tolerance"?
What would an indirect allowed variation mean? There is no such thing.

 

[3DDave]

Bssic dimensions have no tolerance. It's the point of them being basic. There is no variation at all allowed to basic dimensions.

Titleblock tolerances are not directly applied to dimensions - that is, one cannot look at a titleblock tolerance and tell exactly how many dimensions it applies to; one has to infer which they apply to by reading the entirety of the drawing; but by definition alone the committee says they are direct.

In fact, a titleblock tolerance might apply to no dimensions on a drawing at all. That's as indirect as can possibly be. (Pause for a second. Do you know what a "trick question" is? I mean, has that term come up before? Maybe it's a colloquialism you are unfamiliar with? If so, I cannot help with that.) That's what makes it a trick question.

If there is no indirect tolerancing then why is there direct tolerancing?