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?

 

[dtmbiz]

BTW, as a reminder

 

[CheckerHater]

dtmbiz,
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

 

[pmarc]

No offence guys, but am I the only one here who thinks that this thread should have ended on 1 Apr 16, exactly at the moment when para. 2.1.1.2 from the standard was quoted?

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.

 

[dtmbiz]

CH
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.

 

[CheckerHater]

No offence guys, but am I the only one here who thinks that this thread should have ended on 1 Apr 16, exactly at the moment when para. 2.1.1.2 from the standard was quoted?

First, it is not nice to pat oneself on the back.
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

 

[CheckerHater]

Basic dimensions derive tolerances from the applicable FCF.

So, are they derived from "the applicable FCF" or "customary gage tolerances"? Cannot be both...

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

 

[pylfrm]

I agree that the original "UNTOLERANCED DIMENSIONS ARE BASIC" question was answered long ago.

As for the still-burning fire of whether basic dimensions are untoleranced...

Each dimension shall have a tolerance, except for those dimensions specifically identified as reference, maximum, minimum, or stock (commercial stock size). The tolerance may be applied directly to the dimension (or indirectly in the case of basic dimensions), indicated by a general note, or located in a supplementary block of the drawing format. See ASME Y14.1 and ASME Y14.1M.

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:

tolerance: the total amount a specific dimension is permitted to vary. The tolerance is the difference between the maximum and minimum limits.

true position: the theoretically exact location of a feature of size, as established by basic dimensions.

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

 

[dtmbiz]

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)

 

[JNieman]

re: 6) You can lead a horse to water, but you can't make it drink.

 

[CheckerHater]

Shouldn't it be

7)...Profit!

?

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