ASME Y14.5 standard for Reference Dimensions?

[blades741]

I couldn't find anything in the ASME Y14.5-2009 standard that governs the identification of reference dimensions. True, they are most commonly identified with parenthesis (1.250), but is there anything that controls this by way of actual standard?
The real application to my question is in checking a drawing, where the notes state:
1. INTERPRET DRAWING PER ASME Y14.5-2009
2. DIMENSIONS IN PARENTHESIS FOR REFERENCE ONLY

I'm trying to find out if note 2 is redundant, based on note 1.

Thanks for any input on this!

- Bill

 

[lifttrucks]

ASME Y14.5-2009 section 1.7.6

"The method for identifying a reference dimension (or reference data) on drawings is to enclose the dimension (or data) within parentheses. See Figs. 1-19 and 1-20."

 

[blades741]

Tank you lifttrucks, not sure how I missed that!
- Bill

 

[CheckerHater]

liftrucks beat me to it

As a consolation, similar statement from ISO 8015:2011
...
8 Rules for statements in parentheses
Statements given in parentheses are only for information and do not constitute an integral part of the
specification/requirement.
...

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

 

[TheTick]

What the standard does not tell you is there are scads of people who do not know about reference dimensions.

 

[blades741]

LOL, I find myself in a "we've always done it that way" sort of shop. I'm also trying to convince them that they don't need either note because it's an electrical drawing.

 

[JNieman]

I will second TheTick.

I actually stopped myself from posting a comment asking if you think the redundancy is bad. Just because it's covered in the Tome of ASME Y14.5 doesn't necessarily mean it's not valuable to place a specific comment in the notes reiterating something. For instance, I had dealt with someone asking for relief on a dimension they couldn't hold within tolerance. They were within the true position but couldn't get the linear location to work out right because it was so much tighter. It turned out they were applying the dimension tolerance from the "Unless Otherwise.." note, to a hole because of a BASIC dimension. So while they understood the feature control frame, they apparently didn't come across BASIC dimensions often enough to remember how to interpret them.

I've had the same happen regarding reference dimensions more than once, as well, even on drawings in the past that were suffixed "REF" instead of parenthesis.

Sometimes it can save time, confusion, hassle, and response-times just to have a little "risk avoidance" in a redundant comment. Just my 2 cents.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[blades741]

Point taken, JN. The "ounce of prevention" thinking comes into play here. I will be sure to let them know that it's not "wrong" to have note 2 in place, just redundant.

 

[Tunalover]

I avoid reference data entirely. What's contained within parenthesis is only fluff and does not constitute a requirement. Some people erroneously use the reference information to tell them what needs to be; that is they don't understand that the information is just fluff and that they need to look elsewhere for hard requirements.



Tunalover

 

[KENAT]

Minimize use of reference dimensions, but never say never;-)

Posting guidelines faq731-376

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(probably not aimed specifically at you)
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[blades741]

I use them on nearly every assembly print (small tool assemblies) at the assembly level, where they are essentially L x W x H "self-fulfilling" dimensions (I saw that term used here within another thread on reference dimensions, and thought it captured the meaning quite well). I also use them at the detail level, if the intent is to use "stock size", although I'm still debating with myself if that's really a legitimate application.

 

[ewh]

I think it is a mistake to add such redundant information in the notes because it opens the question of which other aspects of the standard may or may not apply.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[KENAT]

I'll also sometimes add them to assembly drawings to people dealing with it have a feeling for the size.

In fact back in the days when I have to have deliverable items NATO codified it was essential to have the overall dimensions indicated.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Gilmiril]

The company I work for insists on using REF to indicate reference dimensions. I've given up on trying to convert to ().

 

[JNieman]

Using REF is still insanely common, I find, even in major companies that proclaim adherence to ASME Y14.5 of some flavor or another. I assume it is in their own company standards that they allow for the use of REF or maybe their "unwritten" standards

If you're a company that doesn't plan on your prints being used outside of a very-majorly English speaking country then I don't think it will cause unintended consequences, at least. Otherwise...

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[3DDave]

Odd thing - in accounting (x.xx) is a negative number. REF is always reference. I think accountants established their standard before ASME had a shot at it.

 

[ModulusCT]

Minimize the usage of reference dims... If they're helpful for someone in some way, go ahead and put them on, but the standard shows them indicated with parenthesis.

Please, please, please, use the correct terms!They're Datum Features NOT DATUMS!!! AAAAAHAHAHAHHAHAHAHHAAAAA" -- Don Day