UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
(OP)
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?





RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
"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."
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
Thanks to you all, Diego
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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,
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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-Toler...
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
Thank you for book reference.
Pmarc
You got it
Hope you have a nice weekend guys
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
No, they are not. It's Saturday and I am not starting this discussion
Another discussion I don't want to start
Absotively posalutely definitely not
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
However, features dimensioned with basic dimensions have a tolerance.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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 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
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
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.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
BTW, as a reminder
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
You posted exactly this:
"I believe I saw in past ASME Y14.5 versions prior to 2009, that basic dimensions are in reality associated to customary gage tolerances."
I have copies of 1966, 1982, and 1994 versions. Where exactly can I find statement to support your point?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
As somebody (I guess it was powerhound) mentioned in one of previous threads, there are aren't many places in the Y14.5 where the committee clearly/directly forbidden something, but in this case it is in black and white. It is has been explicitly stated that mixing general +/- tolerances with the UNTOLERANCED DIMENSIONS ARE BASIC note is not allowed. Period.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
In this case "I believe" is a "I'm not sure"
If you have the standard, and it's not there, I take it it's not in 1973 either and I'll take your word for it
It may have been in a neumman or one of the other training books, not sure.
I'll try and find it.
However in the context of gage design, a Basic Dimension would have to be made like any other gage feature according to standard customary gage tolerances.
It might be presented that there is no dimension that doesn't have an associated tolerance. It's unclear to me why y14.5 defines basic dimension as theoretical exact.
Dimensions on engineering drawings have a local tolerance, a general tolerance or some specification tolerance. The actual dimension is the measurement, distance, size. Basic dimensions derive tolerances from the applicable FCF.
The only exception I can think of is
a reference dimension.
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
Second, you said it yourself, it was posted on April 1st, so I guess, no one took it seriously
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
As for the still-burning fire of whether basic dimensions are untoleranced...
I think the wording here is very unfortunate. It goes directly against the concepts explained in the rest of the standard where basic dimensions are concerned. I basically consider it a mistake, and ignore it.
For example, consider the following:
A positional tolerance defines a zone centered on the true position. If basic dimensions are permitted to vary, then the zones can move relative to the datums. How much can they move? The only answer that makes sense is zero.
For another example, see ASME Y14.5-2009 Fig. 4-50. There are four basic dimensions, and three of them don't relate to part features at all. Why would these have a tolerance? Sure, a real-world inspection method will involve some inaccuracy, but that doesn't mean the dimensions themselves have tolerances.
- pylfrm
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
1) Post was April 1
2) Calculate virtual condition- tolerance from FCF
3) Calculate distance between virtual pins for gage - "standard" gage tolerance
4) Stating that there is a "right answer" to GDT is like stating there is a "right answer" to the alphabet
5) This forum has never been about ending when "it should have". Discussions end for "you", when "you" stop participating".
6) A person convinced against his will, is a person unconvinced.
7)
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
RE: UNTOLERANCED DIMENSIONS ARE BASIC note in drawing
7)...Profit!
?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future