UNTOLERANCED DIMENSIONS ARE BASIC note in drawing 2

[ashivu123]

According to ASME standard shall I use UNTOLERANCED DIMENSIONS ARE BASIC When position and profile of surface specified in drawing to indicate corresponding dimensions are basic, in order to avoid rectangular box for dimension. Drawing also few dimensions which don’t have GD&T and apples title block (+/-) tolerance. Does note UNTOLERANCED DIMENSIONS ARE BASIC conflict in this case when drawing had GD&T tolerance and +/- tolerance?

 

[pmarc]

From ASME Y14.5-2009:

"2.1.1.2 Basic Dimensions. Basic dimensions may be indicated on the drawing in the following ways:
(a) applying the basic dimension symbol to each of the basic dimensions. See Fig. 7-1, illustrations (a) and (b).
(b) specifying on the drawing (or in a document referenced on the drawing) a general note such as: UNTOLERANCED DIMENSIONS ARE BASIC. See Fig. 7-1, illustration (c).

NOTE: Where using this method a plus/minus general tolerance is not allowed."

 

[drawoh]

ashivu123,

As noted by pmarc, it is legal as per the ASME Y14.5.

I prefer to box my basic dimensions. Any dimension on my drawings that have not been boxed and that do not have applied tolerances, are not under control. My drawing is not complete.

--
JHG

 

[patdh1028]

This note, in my interpretation, doesn't make any sense if you have a tolerance block that is giving a tolerance based on, say, number of decimal places shown. We had this note on the block, and we also had a tolerance block. The thing is, the tolerance block is for the stated purpose of of providing tolerances to otherwise not-toleranced dimensions.

I still use a tolerance block on a drawing sheet, but removed the note. I use tolerance block tolerances on dimensions for features of size only, and use explicit basic dimensions (dims with the basic box around them) for location dims or any other dimension that is toleranced without using the tolerance block.

As far as interpreting the drawing you have, it's my understanding that the tighter tolerance wins. And I say that only because that is how I understand the standard, which does allow, for instance, profile of a surface with an "ALL OVER" symbol to basically establish a worst-case variance of an entire part, to co-exist with refining tolerances that establish tolerance zones within the tolerance zone of the all-over control. Very likely that is not what the designer is thinking, he is probably thinking a geometric control overrides a block tolerance always, but the use of the "UNTOLERANCED DIMENSIONS ARE BASIC" note on his drawing has allowed ambiguity into the interpretation of his drawing.

 

[CheckerHater]

It's amazing how people manage turn things inside-out.

The UNTOLERANCED DIMENSIONS ARE BASIC note is used when MOST dimensions on your drawing actually MUST be made basic.

Imagine rectangular plate with 200 different holes in it. The width and length of the plate can be directly toleranced, but locations of all the holes must be made basic with appropriate position tolerance applied.
Here the note UNTOLERANCED DIMENSIONS ARE BASIC saves you time and protects from missing basic frame somewhere.

But I can imagine someone making note part of tolerance sticker because "basic dimensions, they are like really accurate". This is probably the situation patdh1028 is concerned about.

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

 

[patdh1028]

The core of my own confusion about UNTOLERANCED DIMENSIONS ARE BASIC is what is an "untoleranced" dimension? If your drawing has a tolerance block, aren't all the dimensions toleranced by the block unless specifically noted otherwise? That's what's ambiguous to me; the issue with the OP's drawing is something like the hole locations or whatever have TWO tolerances (one from the block applied to non-basic location dims and one from a positional callout), not zero. The question then is (as OP stated) which tolerance is valid? The UNTOLERANCED DIMENSIONS ARE BASIC note isn't very helpful, because a basic dim is untoleranced, not the other way around.

I'd bet CheckerHater is correct about the origin of the note: designers and drafters being lazy and not wanting to draw a box around many location dims. That'd be understandable in the pencil + paper days, but there's little excuse while drafting electronically.

 

[JNieman]

patdh1028 - that's /why/ you _shall not_ have a tolerance block when you note that untoleranced dimensions are basic. This is a binary definition, they do not mix. This was already stated by pmarc who even bolded that part of the section he copied from the standard.

An untoleranced dimension is one without direct tolerances applied specifically to the individual dimension.

It's not about laziness. It's about drawing clarity, ease of configuration management through future revisions, and clutter.


/edit/ fixed typos

 

[CheckerHater]

patdh1028, would you call users of ASME standard "lazy" because they made Rule 1 default, instead of specifying Envelope requirement with every dimension separately?

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

 

[DiegoLGraves]

On the drafting side of my job I may be lazy, but never intentionally sloppy or incomplete. Lazy includes using templates and automating information transfer to drawings through intelligent modelling practices, and understanding design and standards' requirements (to the limit of my capabilities) so I don't waste my time or other company resources. And lazy includes reading this forum so even towards the end of my career the quality of my work improves through increased understanding from discussion input.

Thanks to you all, Diego

 

[dtmbiz]

Its Friday and CH commented:

So,
A note ”Untoleranced Dimension are Basic” can be confusing if taken literally because
In reality dimensions that do not have a local tolerance associated to them, are intended to be toleranced by a general tolerance block per the value relative to number of decimal places.

I have seen metric drawings that try to use the general tolerance block method. Drop trailing zero’s and see how that works for you.


Technically a basic dimension is not “untoleranced”, even though Basic Dimensions are defined in ASME Y14.5 as:

1.3.23 Dimension, Basic
dimension, basic: a theoretically exact dimension…..
…technically, technically they are toleranced too. We do live in a real world, not theoretical. I believe I saw in past ASME Y14.5 versions prior to 2009, that basic dimensions are in reality associated to customary gage tolerances. Do not find in 2009, maybe something in Y14.41. Don’t have it.

Happy Friday,

 

[JNieman]

@dtmbiz

There are some pretty good books out there that I think you would benefit from. In my earlier years, I found a book by David A Madsen to be very helpful and over the years, I've had many people borrow the book with positive replies. Our quality manager here liked it so much he bought himself the exact same book to keep for reference. I find the illustrations, especially the exaggerated tolerance zone explanations, to be very helpful in communicating to coworkers when there is confusion over requirements. It has a very good definition of terms and names too, I believe.

This is the old book, for which he's written new ones for more recent revisions:

http://www.amazon.com/Geometric-Dimensioning-Tolerancing-David-Madsen/dp/1566379776

 

[pmarc]

Oh man...

 

[dtmbiz]

JNieman
Thank you for book reference.

Pmarc
You got it

Hope you have a nice weekend guys

 

[CheckerHater]

In reality dimensions that do not have a local tolerance associated to them, are intended to be toleranced by a general tolerance block per the value relative to number of decimal places.

No, they are not. It's Saturday and I am not starting this discussion

Drop trailing zero’s and see how that works for you.

Another discussion I don't want to start

I believe I saw in past ASME Y14.5 versions prior to 2009, that basic dimensions are in reality associated to customary gage tolerances.

Absotively posalutely definitely not

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

 

[Belanger]

Technically a basic dimension is not “untoleranced”...

Not to pile on, but basic dimensions ARE indeed untoleranced.
However, features dimensioned with basic dimensions have a tolerance.

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

 

[mkcski]

Wow... lots of words. Let me add my two cents. My understanding is: Assuming there is a note on the drawing that says interpret per Y14.5-2009; when you add the UNTOLERANCED note the title block tolerances become null and void because they apply to untoleranced dimensions as well. Given this the tolerance on non-BASIC dimensions must be placed on the field of the drawing so there is no confusion. Also, as I understand it, there in no support in 2009 for location using coordinate dimensioning. So location dimensions should all be BASIC anyway and only size toleraces have direct toleacneing

Regarding tolerance on BASIS Dimensions: Every characteristic of the standard that is theoretically "perfect" (datums, BASIC location, profile dimensions) must be simulated in the physical world by processing equipment. For example - BASIC dimensions for location are simulated by machine tool movements in manufacturing and CMM movements in inspection. The "tolerance" on the BASIC dimensions themselves becomes the positioning precision/accuracy which the machine tool/CMM exhibit. Although not a standard, this accuracy is typically assigned to 10% of the position tolerance in the Feature Control Frame. Comments please.

 

[CheckerHater]

Basic dimensions are defined as "theoretically exact"

I've never seen interpretation of "exact" as "allowing deviation, tolerance"

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

 

[dtmbiz]

mkcski

You seem to understand where I was going with that.

CH

Make a part, even a gage using the most precise equipment known to man using basic dimensions and show me that there is not "tolerance" involved for both manufacture and inspection.

Of course dimensions that are directed to the general tolerance block are toleranced, the tolerance is in the legend near the title block usually, and not locally associated to a specific dimension.

My comments were basically involving a little trivia / something to consider.

I was not speaking of "document text" or mathematical terms.
I was speaking of planet earth were I believe we all live, and then again, maybe not
I was commenting mostly because your comment made me laugh.

You topped that with: I like that [quote="pasalutely"...][/quote] what kind of beer is that ? I want to try some

In reality, the only thing wrong with ASME Y14.5 is the human mind

 

[JNieman]

I think you're mixing up real parts and drawings which contain perfect or exact definitions. I believe Belanger touched on this point by stating:

basic dimensions ARE indeed untoleranced.
However, features dimensioned with basic dimensions have a tolerance.

I don't think you are particularly wrong on anything, dtmbiz, however I do believe you're incorrectly applying terms which causes miscommunication. You're not talking apples to apples with the ASME standard.

You're also misapplying the term 'tolerance' to machine flaws or calibration. Not accounting for the backlash in a lead screw is not a tolerance on your part/print. They are completely unrelated. You're conflating unrelated issues by trying to say basic dimensions have a tolerance because nothing in life is perfect.

 

[dtmbiz]

JNieman

Communication is the essence of engineering.

For the purposes of defining a basic dimension in Y14.5 "theoretical exact" is used.


There seems to be this casual swapping out the use of "theoretical exact" with "untoleranced"
Now I call that "misapplying". The "word swap" does not do a thing to help communicate the intent of the standard that needs to be applied in a "practical sense". Yes, discussion of basic dimension tolerances comes at another level, for instance gage design and is probably best discussed in a different conversation.

If one wanted to apply the definition of Y14.5's basic dimension to produce a gage, then there
are those dirty little gage tolerances that become involved. And not for a part definition tolerance stack... And of course the feature on the drawing derives its tolerance from the FCF that applies to it.

With the exception of concern for swapping out one term for another that are not synonymous, the rest of the comments that have been discussed regarding my comments don’t really benefit the understanding of GDT fundamentals. Just a another layer to the onion.

The only place in Y14.5 (2009 at least) that "UNTOLERANCED DIMENSIONS ARE BASIC" is used is
to describe an option as to how to identify basic dimensions that are not boxed or noted as "basic".
That does not mean that the basic dimension is untoleranced. Again a basic dimension is
"theoretically exact".

Not confused, not mixing anything up, not misapplying tolerance with machine flaws or calibration

Calibrate = adjustment so that it can be used in an accurate and exact way

Flaw = a defect in physical structure or form

(engineering) Tolerance = a permissible variation or allowance to allow part / assy function

Never have seen a "perfect" (flawless) drawing (backlash is perfect example). Hopefully the engineering drawing calls out an engineering specification to cover that. There are many "engineering drawings" that default to customary process (e.g. machining) standards.
Personally don’t like that, but they do exist.

We probably agree to disagree.