Datum Feature Symbol

[GreenMindmn]

Hello I have searched the wide-wide web along with some books and have fallen short to an answer.

My questions is as followed:
What standard does the [-A-] datum feature follow? Meaning the dashes specifically, and if the dashes have any meaning?

http://www.engineersedge.com/gdt.htm

gives the following explaination:
"Datum Identification frame (Symbol) - The datum identification frame (symbol) contains the datum reference letter in a rectangular box, usually preceded and followed by a dash (any letter except I, O, or Q)."

To my knowledge, ASME Y14.5M-1994 says that a datum feature symbol is [A] with a 60deg triangle for a "arrowhead".
I am unsure of the ISO equivalent for GD&T.
So to sum it up, is it best practice to include dashes before and after datum letter, or not to?

 

[ewh]

That was the standard per ANSI Y14.5 (pre ASME Y14.5-1994).

 

[ctopher]

The drafting standards should be taught in college, and every company should have a set.

http://WWW (World-Wide-Web)

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

 

[GDTGUY]

The datum feature symbol was changed from the rectangular box containing a letter preceded and followed by a dash to the "suction cup" symbol with the release of ASME Y14.5M-1994. This change in symbols was done toward harmonizing U.S. standard symbols with those used under ISO conventions.

If you have a copy of ASME Y14.5M-1994, you will find an explanation of the change in Appendix A, "Principle Changes and Imprrovements"; specifically under paragraph A5.

GDT_GUY

 

[GreenMindmn]

I was taught ASME Y14.5m-1994 in college. But my company has an old set of standards. Thus is why I am trying to interpret if this datum was an ISO standard or just an old standard.

 

[ctopher]

I see.
The datum you state is per ANSI Y14.5M-1982.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

 

[CheckerRon]

As GDTGuy said, the boxed datum symbol with a "suction cup" to hang on datum line, is th? ISO datum symbol that ASME adopted in 1994. Many of us still think the "suction cup" is a dumb, unnecessary european thing, but were stuck with it. Do yourself a favor, Green, and get a copy of ASME Y14.5-1994M and use it, before it too is obsoleted.

 

[fcsuper]

The dashes only serve to show that the letter in the box is not its own geometric tol. They don't have any meaning beyond that. As stated above, it's a ANSI Y14.5 1982 thing that has been changed in ASME Y14.5M-1994.

The standards are inexpensive to purchase. There's been a lot of improvements in ASME Y14.5M, so I'd recommend purchasing the new standard and to start using it. Just an idea.



Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[KENAT]

http://catalog.asme.org/Codes/PrintBook/Y145M_1994_Dimensioning.cfm

List Price: $145.00

Inexpensive, maybe from a company point of view if you have a reasonable budget for that type of thing.

From a personal point of view, that's quite a bit. I still haven't recovered from paying 70+ for Rourke!

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

LOL KENAT, I was talking about from a company POV. However, I do spend that kind of money on my own library from time to time. Speaking of which...

What do you think of Rourke when compared to other similar books out there. I'm am looking to making a purchase and been looking around, but been seeing mixed comments about whats available.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[KENAT]

I figured you meant from a company point of view but I know some people spend a lot on these types of resource.

Honestly I'm not much of a stressman, Rourke was what the chief stressman and a couple others used at my last place and that was a good enough recomendation for me.

It's probably off topic for this thread but I have seen a thread(s) asking about this type of thing. Can't remember which forum it was; Mechanical engineering other topics or somewhere in Structural Engineers I think. Sorry I can't be more help.



KENAT, probably the least qualified checker you'll ever meet...