This is what I mean by misrepresenting the subject matter. 1

[3DDave]

https://www.youtube.com/watch?v=dtlLIllpl1w&feature=youtu.be&t=660

What does the teacher indicate is GD&T? He slaps the feature control frame. As if they are the same thing. Earlier he basically says that GD&T is a subset of Y14.5, starting some 20 pages in after the definitions and rules.

This is why it's important to stamp out the 'GD&T' concept and replace it with the names given in the standard. There is no definition for it and users just make up whatever they think it means, which is not a common language, but like the fall of the Tower of Babel.

 

[KENAT]

3DDave, I congratulate you on having such an awesome career and life that this is so high on your "things to worry about list" that you hijacked one thread to pontificate on it and then started another thread to take it even further.

However, do you have to rub out noses in how great your life/career is.

Posting guidelines faq731-376

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

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

 

[JNieman]

There are geometric dimensions and standards of applying and interpreting them.
There are geometric tolerances and standards of applying and interpreting them.

Geometric Dimensioning and Geometric Tolerancing is rather redundant, don't you think?

I see and hear people slightly misinterpreting the nomenclature semi-often in the real world but guess what... everyone knows what everyone is talking about, and when disagreements or confusion is introduced, there is a written standard that clarifies things and then we all move forward on the same page.

I bet you can't handle it every time someone says "ATM Machine"

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

 

[3DDave]

Kenat, If you watched the video more you would find he later gets circularity wrong, saying a circularity of .001 would mean an ovoid section could vary from X to X-.001 in diameter at the tolerance limit. Pretty much, when someone says GD&T it ends up there is a noticeable gap in their understanding in an area they claim familiarity with. And I believe the reason is they didn't read and understand enough to be bothered by the fact that "geometric dimensioning" is not defined or described. Unless you would accept someone selling cars and calling them Ford Corvette or a Kia Mustang. Because you know what they mean, right?

JNieman, pretty sure there are no geometric dimensions. Good luck finding it defined in any version of Y14.5. Also good luck finding a distinguishing characteristic that separates 'geometric dimensions' from 'non-geometric dimensions' in the area of dimensioning, tolerancing, and drafting.

 

[pmarc]

Pretty much, when someone says GD&T it ends up there is a noticeable gap in their understanding in an area they claim familiarity with. And I believe the reason is they didn't read and understand enough to be bothered by the fact that "geometric dimensioning" is not defined or described.

Dave, please take a look at following websites:

http://www.etinews.com/index.html

- A. Krulikowski's business;

http://www.geotolmeadows.com/index.htm

- J. Meadows's business;

http://www.tec-ease.com/

- D. Day's business;

https://www.geotol.com/

- A. Neumann's business;

https://www.advanceddimensionalmanagement.com/

- B. Fisher's business;

These are companies established/owned either by members of the Y14.5 subcommittee or members of the support group. The "GD&T" appears on every single home page. Are you trying to say that these guys do not really understand what they claim they are familiar with? Are you implying that "they didn't read and understand enough to be bothered by the fact that "geometric dimensioning" is not defined or described"?

I hope you at least don't think the teacher from the youtube link made that circularity mistake because he had used "GD&T" so nonchalantly ;-)

 

[JNieman]

I was speaking generally when I stated 'geometric dimensions' as a purely logical application of the words.

I don't need the word "geometry" defined for me in ASME Y14.5. Suffice to say, there are a great many words I do not need defined for me in ASME Y14.5 because my knowledge of those words is derived elsewhere. I think a generous application of such common sense would suit this topic well.

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

 

[CheckerHater]

If I am allowed to add my splash of kerosene to the fire, could we agree, for example, that "Geometric dimensioning and tolerancing" is a SHORT way of saying "Dimensioning and tolerancing of geometrical features"?

Would that be to much of a stretch of English language?

After all, both ISO and ASME are seeing parts being made up by features and said features have geometry - they are planes, cylinders, cones, etc., etc.

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

 

[pmarc]

For what it's worth, I think the term "GD&T" is so popular, despite the fact it has not been clearly defined in any standard, because it is commonly understood as a kind of dimensioning and tolerancing that uses datums, feature control frames, and other related concepts as opposed to the old-fashioned dimensioning and tolerancing style that is solely based on directly toleranced linear and angular dimensions.

Regarding CH's suggestion, I agree that the "Dimensioning and tolerancing of geometrical features" can be a long way of saying "Geometric dimensioning and tolerancing". I am just wondering... Doesn't it fit to the old-fashioned D&T as well?

 

[ewh]

That's my position as well... be it directly toleranced linear and angular geometry or geometry which is defined by basic dimensions and controlled by specified feature tolerances, the goal is still to define the geometry required to make the item. After all, it is not a huge leap from geometry to geometric.

ge·o·met·ric (adjective)
of or relating to geometry, or according to its methods.

ge·om·e·try (noun)
a branch of mathematics that deals with points, lines, angles, surfaces, and solids

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

 

[Belanger]

How about this -- maybe it's called geometric dimensioning and toleranceing not because it's tolerancing geometrical features (I agree that the traditional method attempts to do that too) but because it applies tolerances that are themselves based on geometries: flatness, straightness, parallel/perpendicular, etc.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[axym]

Hi All,

I agree that "geometric dimensioning" is not defined in the standard and the term was probably not intended. It's dimensioning and tolerancing of geometry. In hindsight, "dimensioning and geometric tolerancing" might have been a better term.

The thing that distinguishes geometric tolerancing is the use of tolerance zones. So "zone tolerancing" would be more descriptive.

Even better, we could have had Dimensioning And Feature Tolerancing. "Did you hear that Y14.5 has released another DAFT standard?". "Take it easy, those guys are doing the best they can".

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca