Trick questions 1

[3DDave]

Per the 2009 version:

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

 

[ctopher]

The title block tol is for all dimensions that are not indicating tol.

ctopher, CSWP
SolidWorks '17
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[3DDave]

Yes, that is true, but that is not an answer to either question.

 

[ctopher]

Title block tol is a direct tol. I'm not clear what you mean by indirect tol.

ctopher, CSWP
SolidWorks '17
ctophers home
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[3DDave]

A tolerance that is not a direct tolerance.

 

[CheckerHater]

It depends on standard you are using.

1994 standard was more or less clear:
Limits and directly applied tolerance values are specified as follows.
(a) Limit Dimensioning. The high limit (maximum value) is placedabovethe low limit (minimum
value).
(b) Plus and Minus Tolsrancing.The dimension is given first and is followed by a plus and minus
expression of tolerance.

2009 standard added:
(c) Geometric Tolerances Directly Applied to Features

While still trying to exclude basic dimensions:
The tolerance may be applied directly to the dimension (or indirectly in the case of basic dimensions)

2018 standard doesn't care about indirect tolerances at all.

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

 

[3DDave]

Those are direct tolerances - so why was it necessary to call them direct if all tolerances are considered "direct"?

That's what makes it a trick. The committee went out of their way to create "direct" tolerances but then classified all tolerances as "direct."

Basic dimensions have no tolerance. That statement must be so they can try to fail another test taker of the GDTP exam.

 

[drawoh]

3DDave,

Why can't I write a note on a title block to state that all untoleranced surfaces are to be a 0.5mm profile with respect to the datums?

--
JHG

 

[greenimi]

3DDave,

That's a swamp. I think has been discussed, at least partially here

https://www.eng-tips.com/viewthread.cfm?qid=467965

What do you think? Anything you don't agree with?

 

[3DDave]

drawoh - you can. The question is why define "direct tolerances" when there is no alternative such as "indirect tolerances"?

 

[drawoh]

3DDave,

That is the way it has always been done. How many people out there are using title blocks designed in the last ten years?

--
JHG

 

[3DDave]

drawoh - "why was it necessary to call them direct if all tolerances are considered "direct"? "

Or is your question just to hijack to a different topic entirely?

 

[drawoh]

3DDave,

???

If your title block has a note stating that, unless otherwise specified, all untoleranced dimensions are basic, and that the profile tolerance is 0.5mm WRT datum features[ ]A, B, and[ ]C, it is very recent. This is not how they did it back in the day.

If your title block is thirty years old and you are using ASME Y14.5[‑]2018, you need to dimension your drawing fully.

--
JHG

 

[3DDave]

Drawoh - you are trying to deal with a far different problem and I don't know why.
I have written nothing like what you just claimed.

If I put on the ASME Test - "What is an indirect tolerance?"
What would your answer be?

 

[greenimi]

I agree with 3DDave, drawoh is bringing a totally different issue than the one raised by the OP.

Also, drawoh is brininging AGAIN the unless otherwise specified known issue (which issue has been discussed here many times)

 

[greenimi]

3DDave,

Did you read my previous referenced thread ? pmarc and Evan participated in it.
I would say it is touching the issues you brought up in this discussion. Don't you agree?

 

[CheckerHater]

This is the same problem like with many, many other aspects of Y14 - lack of definitions.

The dichotomy direct / indirect may be interpreted differently, thus the ambiguity.

First, it may have "hierarchical" meaning - is tolerance related directly to dimension, or thru "middle man" of a sort. Like position tolerance does not apply directly to basic locating dimension, but is used together with size dimension and tolerance to build virtual condition - the complete description of where hole can and cannot be. In this sense geometric tolerances are indirect (although 2009 claims they are direct).

Another, more simple interpretation is where tolerances are located on the face of the drawing. If they are attached "directly" to dimension, they are "direct". In this case title block dimensions are "indirect". Naturally one can argue, the dimension DIA 12 H10 has exactly the same meaning as dimension DIA 12 combined with title block note "UNTOLERANCED DIM'S ARE h10".

Now you put together committee of 10 people having 10 different definitions of "direct" and we have what we have.

There is no need to look for a "trick" when you can have simpler explanation.



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

 

[3DDave]

If not being attached means they would be "indirect" then that would imply a difference in the way the user should evaluate their contribution -numerically- . That is, that they count more or they count less than direct tolerances. What else would be the effect of a hierarchy? But I don't recall seeing a separate column for "direct" and "indirect" tolerances in tolerance stack analysis.

It remains that the '2009 standard fails to define explicitly any example of "indirect" tolerances while it classifies ALL tolerances as "direct," regardless of where they are on the drawing. And if all tolerances are "direct" why use the additional adjective in the first place?

That's what makes it a great trick question.

greenimi- I am sorry. I originally didn't realize that it came across a problem with the terminology. It started with the premise of "unless otherwise specified" and the first dozen replies were all about that. Meandering discussion poses a problem that way. It seemed to drift around how tolerances are applied, though it does note that this problem is apparently the direct result of committee meddling with the definitions to be all things to all people, as noted by:

Recently, almost any feature can be considered as directly toleranced. I think it had something to do with irregular features of size, and the desire to include irregular features controlled by a profile tolerance as "directly toleranced" in order to meet the definition of feature of size.

Which leaves the original problem - that "directly toleranced" no longer has a useful meaning.

 

[drawoh]

3DDave,

You asked if the tolerance on the titleblock is a direct tolerance. I claim that it depends on what tolerances you called up on the titleblock.

--
JHG

 

[3DDave]

Drawoh - it appears that ALL tolerances are direct tolerances. That's the trick to that. There are no indirect tolerances defined in the standard, unless one also qualifies that answer to say it depends on the version of the standard, which is a separate trick to the question as that would be about incompatibility of the various versions of the standard.