Basic dimensions - boxed vs. unboxed

[Andera]

If a drawings has a general profile such as "Unless otherwise specified all features or all surfaces PROFILE within xxx to A|B|C|
and
a note "All untoleranced dimensions are basic"
then what would be the difference between boxed dimensions and unboxed ones (with no direct tolerance)?

Is there an industry standard to when use boxed dimensions (to show basic dimensions) and /or when to default to the above note?
If no industry standard then maybe "best practice"?

 

[drawoh]

Andera,

The boxes explicitly indicate that the dimensions are basic. If there is a note that states that dimensions are basic unless explicitly specified otherwise, the box is redundant.

Given that ASME Y14.5 bans trailing zeroes on millimetre dimensions, I find that good drafting practise is to go through dimension by dimension and apply tolerances. I box a dimension after I satisfy myself that the feature is controlled by the appropriate GD&T. Dimensions either are boxed, or they acquire some form of [±][ ]control.

A note stating that all dimensions are basic unless specified otherwise, is a good way to be lazy. If your part is a one-off prototype piece with requirements well within your intended manufacturing process, go for it.

--
JHG

 

[ctopher]

I would never use such a note. I agree, it's lazy.
I note would be overlooked, a box would not.

ctopher, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[dgallup]

Personally, I don't like the general note but definitely don't use the general note and then box some dimensions, that would create confusion which drawings are supposed to avoid.

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[pylfrm]

Andera,

I agree that dimensions shouldn't be boxed on a drawing with a note like that. The redundancy just leads to questions.

I wouldn't call the note lazy though. Certainly not any more lazy than "ALL DIMENSIONS ARE IN MILLIMETERS UNLESS OTHERWISE SPECIFIED".


pylfrm

 

[greenimi]

Gentlemen,
What about this approach:

If a feature is defined with a stand-alone FCF geometrical tolerance then should have its applicable basic dimensions shown and boxed.
If a feature definition goes to the default profile (UOS general profile note) then should have its applicable basic dimensions unboxed (or even taken from the 3D CAD model).

Feel free to shoot holes in my above statements....why do you think that cannot be feasible, what issue would you see, "what if scenarios", anything you can think of....

 

[dtmbiz]

Andera

I agree with you that the note inst necessarily "lazy"; my preference is "boxed"

ASME Y14.5 2009 states note and "boxed" are two ways. Unfortunately it does not state both cannot be used. (one or the other)
I do not know of any industry or ASME standard "when" to use either one way or the other.
I agree with above posts that the "common sense" standard would be that use of both on the sames drawing would be at best "confusing".

The use of the note if there is a general tolerance default note ?

If a drawings has a general profile such as "Unless otherwise specified all features or all surfaces PROFILE within xxx to A|B|C|

Curious note. Nothing comes to mind as to what to apply the profile control to other than a surface, partial surface or elements of a surface.
It also does not refer to Profile of a Surface or Profile of a Line control. (That can be a can of worms-yuck!)

1.3.27 Feature
feature: a physical portion of a part such as a surface,
pin, hole, or slot or its representation on drawings, models,
or digital data files.

 

[dtmbiz]

The use of the note if there is a general tolerance default note ?

should have been;

The use of the "All untoleranced dimensions are basic" note is prohibited if there is a general tolerance default note on the same drawing.

 

[greenimi]

The use of the "All untoleranced dimensions are basic" note is prohibited if there is a general tolerance default note on the same drawing.

dtmbiz,
Could you, please provide more details?
Which paragraph of the ASME states all the above? I am trying to figure that out....
Thank you

P.S. I found only this (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.
(c) For specifying and querying basic dimensions
on models or digital drawings with models, see ASME
Y14.41.

 

[dtmbiz]

Greenimi

It is in your post of 2.1.1.2

Have you ever tried to understand a drawing with both the Untoleranced dimension note and default general tolerance note are present ?

I have run across them in my experience and then the drawing becomes at best subject to multiple interpretations.

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

 

[greenimi]

dtmbiz,

I guess we have to be as specific and as detailed as possible:
The standard states that ± general tolerance (my note 2 PLACES: ±.010, 3 PLACES ±.005, angular tolerances ±1°) and "Untoleranced dimensions are basic" CANNOT be/ is prohibited to be on the same drawing.
That's all is saying and I agree with that.

My question was about your statement:
copy-paste
"The use of the "All untoleranced dimensions are basic" note is prohibited if there is a general tolerance default note on the same drawing."
end of copy-paste

If "All untoleranced dimensions are basic" is KEPT and a general PROFILE tolerance default note is ADDED,
in my opinion these two can coexist very well together, but will contradict your above statement. So, I have requested some clarification from you (edit instead of your)about your statement which I still consider it is misleading at best (as originally phrased)

 

[dtmbiz]

Greenimi

Not sure what is misleading.

ASME Y14.5 2009 states: "NOTE: Where using this method a plus/minus general tolerance is not allowed."

My post states: "All untoleranced dimensions are basic" note is prohibited if there is a general tolerance default note on the same drawing"

Maybe my post sounds confusing to you because "plus/minus" was left out. I should have put it in my post for more clarity.

The default default geometric control note i.e Profile of Surface control (quite permissible) and general tolerance default are different different terms.

Hope that clears up any confusion: default geometric control vs. default general tolerance ? (understood geometric controls contain a tolerance)

 

[dtmbiz]

Greenimi

Would you agree with the principle of not having plus/minus general tolerance at the same time of having "All untoleranced dimensions are basic" note,
would by extension of principle also apply to other default general tolerance notes i.e. UOS .XXX = -.002 /+ .005; or .XXX = -.000 / +.010 or other types of general tolerance default notes?

 

[greenimi]

Would you agree with the principle of not having plus/minus general tolerance at the same time of having "All untoleranced dimensions are basic" note,
would by extension of principle also apply to other default general tolerance notes i.e. UOS .XXX = -.002 /+ .005; or .XXX = -.000 / +.010 or other types of general tolerance default notes?

I am not following what these general notes are:
"general tolerance notes i.e. UOS .XXX = -.002 /+ .005; or .XXX = -.000 / +.010 "

Could you, please explain.

Re:".......other types of general tolerance default notes?"
No, I would not agree if you are to include a general profile note among "other types of general tolerance default notes"

Please also explain what "other types of general tolerance default notes" means.

As I said, is better to be detailed .........if you are asking an overly generalized question you will get an overly generalized answer --copy paste from a different thread

 

[pmarc]

I don't think the approach with general note "All untoleranced dimensions are basic" and unboxed basic dimensions will work well in Model Based Definiton in the cases where basic dimensions must be shown in the definition.

Humans may not have problems with interpreting the untoleranced dimensions as basic, but to machines, e.g. CMMs, they will just be regular dimensions with no/missing tolerances.