The "purpose" for definition of FOS and AME (ASME Y14.5 2009) Conical /Tapered features 3

[dtmbiz]

Unfortunately the ”purpose” for the need to define certain and specific terms and concepts", which would be helpful in determining the “intent” of the standard’s definition regarding inclusion and /or exclusion for features considered in respect to those definitions and concepts. More specifically regarding FOS and AME for this discussion relative to conical and tapered features.

Here are my general points for discussion. I hope others will post theirs.

Purpose of FOS: (Feature of Size) My understanding of its purpose is to identify features that have center planes, axis and center points in order to locate and orient tolerance zones.

Purpose of AME: (Actual Mating Envelope) My understanding of its purpose is to establish a produced FOS’s actual location and orientation of it’s center plane, axis or center point by use of a AME Datum Simulator (gage) in order to verify compliance with the defined tolerance zone by comparing the true feature's vs. the produced feature's location and orientation of axis, center plane or center point.

It is also my understanding that applied geometric controls to an FOS, “other than size” can only be verified after the produced feature’s has been verified to be within size limits.

Conical and tapered feature’s: In a previous thread (thread1103-460248) there are arguments that conclude that these type features cannot be classified as features of size because in the case of a cone (conical feature) there is a limit to expansion or contraction about the apex, and similarly a limit to intersection of tapered surfaces beyond their intersection.


Disagreement with argument that 'conical and tapered surfaces are not FOSs because an AME cannot be defined":
Conical and tapered surfaces can and do have an AME in the physical world (vs a purist mathematical theoretical world) which can identify a produced FOS axis or center plane.
The AME’s Datum Simulator would not expand or contract beyond the limit of the apex of a conical surface or intersection of tapered surfaces whether or not they actually occurred within the size limits of the feature’s extent. Concluding that the apex of a conical surface and the intersection of tapered surfaces would be to one side of the tolerance limits and would be the minimum or maximum allowance which therefore would be the minimum or maximum limits of contraction or expansion of an AME. (internal / external feature). Expansion or contraction is limited to be within limits of size vs. infinite or unlimited

**** Also would like to mention in relevance to the FOS definitions, specifically around the standard's use of “may”, and the definitions of words ; may, must , will, shall in the engineering environment (English that is). “May” is a permission word that “allows” and is not mandatory. “Shall” is a “mandatory requirement” which is not used in definition of FOS

 

[greenimi]

I doubt that any training company has made a specific statement about the FOS status of cones. Just using them as datum features does not automatically qualify them. The example you posted does not mention the cone as an FOS or IFOS.

Fully agree with this.

All that I have been able to find do teach conical features to be an IFOS.

Well, I asked you 3 days ago about some examples of such (training companies that teach that cones are IFOS). AGI example you provided does not reflect your interpretation. I do not think that is their (AGI's) intent (to teach that cones are IFOS), but I think it is just your misinterpretation.

If you don't mind (and using your provided picture), I will ask AGI on their linkedin group what is the truly intent of the text highlighted by you in yellow --from their Advanced training material--

 

[dtmbiz]

nnosnees fro nnoseens

Fo corseu teh dobtrues nda crticziers hvae on fcat bsade slotiuons. Thye dbout nda crticiize fro the skae fo dobuting nad crtiiciznig bceause thta si thrie ntaure.

 

[greenimi]

nnosnees fro nnoseens

Fo corseu teh dobtrues nda crticziers hvae on fcat bsade slotiuons. Thye dbout nda crticiize fro the skae fo dobuting nad crtiiciznig bceause thta si thrie ntaure

What's this? Hopefully, there is no frustration on your part. Does not worth it. Keep it cool.

 

[dtmbiz]

Good morning Greenmini,

I am not sure what you are referring to that I would be frustrated about?

If that is a projection of how you feel, then you probably should consider what this forum actually is.

E.g. This forum is like a virtual play that unfolds with each post in which anonymous actors reveal themselves.

Entertainment nor the “anonymous actors” should be taken too seriously.

 

[greenimi]

what this forum actually is.

E.g. This forum is like a virtual play that unfolds with each post in which anonymous actors reveal themselves.

Entertainment nor the “anonymous actors” should be taken too seriously.

I am not sure why you came here, but I do to learn. This my only objective and goal. [pre][/pre]
If your are here for entertainment that I guess it is your own option.

I can tell you that is the best forum for this stuff I was able to find (at this time).

 

[greenimi]

And the winner is......

My note: Sometimes being wrong is more rewarding than being correct, as I learn something new from this thread...Thank you. I really appreciate this discussion.. Very very much. And I mean it.



Michael Adcock •
1st degree connection
1st
Dimensional Engineer, Author, Consultant, Trainer
I’m not an AGI trainer, but for a consensus, I agree with Norm and Mark.
ASME Y14.5-2009 figures 4-3 and 4-45 show a cone datum feature provides and axis. Non-features of size - like a plane or arc less than 180 degrees - do not provide an axis.
Also regular (or traditional) features of size had their geometry limited by the definition of a regular feature of size - circle, sphere, cylinder, parallel planes, & parallel lines.
So if a cone is not a regular feature of size but provides an axis....
It’s not a difficult determination.

Mark Foster
Mark Foster •
1st degree connection
Owner, Applied Geometrics, Inc.
Yes, I would contend that a cone is an irregular feature of size. The rationale is that it (the cone) cannot be fully defined by one dimension.

Norm Crawford
Norm Crawford •
1st degree connection
GDTP-S, Model Based Definition Specialist
A cone is considered an irregular feature of size.

 

[3DDave]

As I mentioned in my thread - the definition for irregular feature of size admits all possible features, but it does not hinge on determination of an axis, but its relation to an actual mating envelope.

 

[Burunduk]

Greenimi,
Why are you so quick to declare that you were wrong? You presented a backed up argument for cones not being FOS in your post in this thread from 2 Dec 19 19:46:

"CANNOT contain or be contained by an AME
(...), meaning further contraction IS possible and no AME could be determined".

Do you already dismiss it? Based on what?
Did you try to present the above explanation to these people? I don't see that they provided any detailed justification to their position, at least not anything intelligible that dtmbiz didn't already say here in this thread several times. Fig. 4-3? "provides an axis"? Wasn't all this addressed here already? Irregular because "cannot be fully defined by one dimension?" - This one doesn't even comment on "why FOS?". And yet it seems like you just take their word for it. Why?

 

[dtmbiz]

Greenimi

Personally, for what it is worth, I never considered you as “wrong”. Your posts were based on how you interpreted Y14.5 2009 regarding conical features as FOS.

My previous posts were to point to Y14.5 2009’s purpose for a FOS (either type) which is to define theoretical datums (axis, center plane, center point) and that conical features do by definition have an axis.

Conical features also are contained by an AME. That is a straightforward geometric concept for construction of a perfect similar counterpart about an imperfect produced feature.

I admire your due diligence in order to determine if Y14.5 2009’s new FOS irregular and the examples in Fig 4-3 apply to conical features.

It is certainly a strength to “update” one’s interpretation based on new information that is directly connected to the definitions and principles of Y14.5 2009 from credible sources.

You deserve a “post star” for "valor" (the 1st I have ever given)

 

[greenimi]

Burunduk,
Awhile back, here on this forum, I received one of the best advices from one of the best GD&T experts that come here (from time to time) Evan Janeshewski.

greenimi,
Try not to read too much into the rough classifications that the GD&T standards use.

That being said, I was trying to follow his advice….. meaning the fact the cones are IFOS or are surface feature or are feature of “non-size” (as I initially stated), probably, does not matter.
What matter is the fact should be defined with profile (as the standard shows examples of). At least according to ASME standards (1994, 2009, 2018). Never seen anything else other than profile for the cones (as a standardized definition)
How will be in the future (near future or not so near) remain to be seen….That is why I gave up and that is why I said I was wrong.
After probing it just a little further the AGI expert came back and saying

“Cones are deceptively difficult little critters to deal with, and ASME is, IMO, far behind ISO in standardizing the best practices with regard to defining them, although I know that they (the folks at ASME) are working hard on coming up with a new standard for defining cones better.”
“Position tolerance may be applied on an MMC or LMC basis to any feature of size, regular or irregular, using the surface interpretation of position (which is the default for position tolerances using MMC or LMC modifiers). Applying a position tolerance to an irregular feature of size on an RFS basis would not be a great idea, depending on the specific characteristics of the irregular feature of size in question, because it may be difficult, if not impossible, to define the axis or center plane that is supposed to reside within the tolerance zone. Some irregular features of size DO have a definable axis or center plane, and in those cases, using a position tolerance RFS may make sense”. (Mark Foster, AGI)

 

[chez311]

It seems like only experts having opinions on one side of the argument have been presented here - and even more specifically from one group (AGI).

Let me present the below, a discussion between the aforementioned Norm Crawford of AGI and Evan Janeshewski (axym) of Axymetrix Quality Engineering Inc. and Vice-Chair of the Y14.5.1 committee responsible for releasing the updated math standard Y14.5.1-20xx.

https://www.eng-tips.com/viewthread.cfm?qid=259238

I hope Evan does not mind my mentioning him here - I do so out of great respect for him and his knowledge.

 

[Burunduk]

What matter is the fact should be defined with profile (as the standard shows examples of). At least according to ASME standards (1994, 2009, 2018). Never seen anything else other than profile for the cones (as a standardized definition)

What about this one? From ASME Y14.5-2009:

 

[dtmbiz]

Chez311

Thank you Chez, didn’t realize Norm had posts in EngTips.

Read the thread.

Don’t see any new argument from Axym’s posts which would disprove that a conical feature is an FOS (irregular).
His actually tend to prove that a conical feature is a FOS irregular.
Just seems that he doesn’t like them to be, given the examples that he imports regarding calculations.

In practicality his post admits that these features “work in practice” and goes on to say (IMO) that “he doesn’t like it” regarding his view of its “worth”.

I believe Norm’s posts refuted Axym’s posts nicely.

It could be added that in reference to Axyms question. How about with dimensions ? Volume? Surface area ?

How would you define the size of a cone,…?

If one wants to go off into “theory land” without regard for reality, then it “could be theorized” that a “rectangular box has no size” because it is made of planar features that go off into infinity.
Arguments that refute that a conical feature has size, seem to place no value in solid geometry.

In the context of a FOS within the scope of Y14.5; each geometric element within a FOS, "stand alone" may have no size,
however the collection of geometric elements do collectively create a FOS.
The extent of each geometric element is defined by dimensions that result in geometric limits which together define a feature with size.

 

[3DDave]

I have, for sake of argument, two boxes. Each has linear dimensions that add to the same value.

dtmbiz - are they the same size?

 

[dtmbiz]

3DDave
Each has linear dimensions that add to the same value

Do you mean "Each has a linear dimension that equal the same value" ?

Would like to discuss solid geometry in respect to size regarding rectangular prisms and cones ?
If so, within the definitions of solid geometry it would be useful to compare examples of both.

Hopefully you realize the point is that "theory" can go off into bolivian vs. "Y14.5 has a limited scope that is meant to deal with the reality" of dimensioning & tolerancing imperfect physical features.

 

[dtmbiz]

Burunduk,

Interesting post of a plus/minus defined conical feature.
What is your point ? Just to affirm that it is not required to use geometric controls ?

One of the benefits for applying GDT geometric controls is to remove at least some ambiguity that
plus/minus dimensioning leads to.

How would you advise to “position” (locate and orient) a conical feature defined by plus/minus dimensioning?

 

[Burunduk]

dtmbiz,
It was argued that a cone must always be defined with profile, the figure I posted indicates that apparently, it is not so.
Plus-minus toleranced dimension applied on a feature in the Y14.5 standard is a clear indicator that the feature is treated as a feature of size (it is considered bad practice to apply them on anything else but FOS). Plus-minus toleranced dimensions can also be used as the basis for the application of position tolerance (feature control frame attached to +- toleranced dimension), and tolerances of position apply exclusively to features of size. How to interpret a position tolerance related to a local diameter is another question - hence the concern I expressed earlier relative to lack of examples in the standard (did you find any in your training materials by now?).

 

[3DDave]

dtmbiz - what do you think the point of the example would be if individual dimensions were identical? You make a bad-faith argument. Is that on purpose?

 

[dtmbiz]

3DDave

Accusatory assertions have no value for legitimate discussion of Y14.5

I have no idea of what your point is, that's why I asked the question for clarity.

I have, for sake of argument, two boxes. Each has linear dimensions that add to the same value.

What could that possibly mean ?
"linear dimesions add to the same value"

 

[Burunduk]

Perhaps 3DDave means that one box has width of 3 and height of 7 and the other height of 5 and width of 5?