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

 

[pmarc]

I would have preferred the committee members to do the work to develop a better definition for position tolerance rather than crippling the definition of feature of size, but here we are.

For example, ISO allows a flat surface to have a position tolerance, but the ASME members only want a certain level of compatibility so they don't lose out and get replaced by the ISO. (Why have one training course when you can have three? One ISO, one ASME, and one for differences training?)

This is an interesting thought. If Y14.5 committee members wanted to have full compatibility with ISO, cones and wedges would be features of size. Namely features of angular size.

 

[dtmbiz]

The purpose of FOS is to establish theoretical datums by simulation using physical features

The purpose of an AME is to define an "envelope" for any produced and specific feature based on it's uniquely produced characteristics of size, form, orientation and location.
Which characteristics are required for definition depends on whether the considered envelope is RAME or UAME

A conical feature is a FOS (irregular) supported by ASME Y14.5 2009:
1) Section 4.3 para. (d)
2) Fig 4-3 (previously posted in this thread) constraining 5 DOF’s
3) Primary Datum Feature Fig.4-2 & 4-3

Logic would apply that if the size and extent of a conical shaped tolerance zone can be defined (Section 7.4.3 & Fig 7-27)
then it stands to reason that size and extent of a physical feature with a conical shape can be defined as an FOS.

A conical position tolerance zone is specified by
different position tolerance values at each end of a
cylindrical feature. A conical tolerance can be interpreted
either in terms of the surface of the feature or
in terms of the axis of the feature

Tapered opposing surfaces equally disposed about a center plane is a FOS, supported by
the addition of definitions with their examples in Y14.5 2009. These feature definitions can
and do establish theoretical datums. They can be used as primary datums.:
1) "Linear Extruded Shape" feature
2 ) "Complex" feature

My earlier consideration of the wording “may” used in 2009 Y14.5 FOS definition regarding an AME,
is now that there is allowance for one of two conditions for a FOS definition which are; “to contain” or “be contained by”.
One or the other is a requirement in order to satisfy FOS definition.

 

[3DDave]

Is a single plane a feature of size? Just because it can be a datum feature does not make it a feature of size.

 

[3DDave]

The difference between considering a conical surface as a feature of size (aside from not having a unique size value/having an infinite number of unique nominal sizes as measured along the feature) and a conical tolerance zone is that the tolerance zone is considered perfect and is compared to the uniquely determined perfect axis of a feature of size.

The only similarity is they share the word "conical."

 

[Burunduk]

It is possible to look at it this way:
A cylinder has a constant nominal diameter, D and an infinite number of actual local sizes as produced.
A cone is defined by the difference of diameters along a unit of length: (D - d)/L, while at any cross-section the nominal D-local is known, and also has an infinite number of actual local sizes as produced.
Both features are defined by diameters (diametrical size), theoretical and measurable. One is nominally constant, the other nominally variable but fully defined.
So where is the critical difference that leaves only one of them a feature of size and excludes the other?

 

[dtmbiz]

It is interesting to me that posts refer to a “single distinguishing size", “unambiguous size”, “unique size” which I would interpret to be a “constant size thru the extent of the feature” ?

If that is what is meant, then those concepts are not included in Y14.5 2009’s definition of FOS. There is no mention of the terms that those posts introduce which could exclude or include feature shapes depending on more specific definition of those terms.

The definition for FOS does include; “…associated with a directly toleranced dimension” for FOS regular type and “directly toleranced feature or collection of features” for FOS irregular type.

If a cylindrical feature is a considered feature within a component’s definition and that cylindrical feature is
produced at MMC at one end and LMC at the other end, then the actual produced feature is a conical feature and that feature’s axis can still be simulated.

If a square or rectangle is a considered feature within a component’s definition and the opposing faces of
either feature is produced at MMC at one end and LMC at the other end then the produced opposing surfaces would be tapered and their respective center planes can still be simulated.

 

[greenimi]

dtmbiz,

For what is worth, I read a little bit your material provided by you (from the AGI Advanced training materials) and I do not think the yellow highlighted text from your book provide “license” of reading and interpreting cones as being feature of size (FOS). I do not think these “pros” (this training company’s trainers) think it is a good idea to apply position to a cone…At least that is my feeling reading your posted excerpts.
Maybe you can apply position to a cone and in that case you are controlling only a circular element and consequently you are concern only about the center point (of a particular circular element) location. That I would say is somehow feasible. But not to the entire cone.

https://www.eng-tips.com/viewthread.cfm?qid=450175

 

[3DDave]

dtmbiz,

"If a cylindrical feature is a considered feature within a component’s definition and that cylindrical feature is
produced at MMC at one end and LMC at the other end, then the actual produced feature is a conical feature and that feature’s axis can still be simulated."

It is simulated with a cylinder. The axis of the simulated cylinder is used to understand the position and the diameter of that simulated cylinder describes the size.

Ever notice that all cones of the same included angle are exactly the same size, perhaps just cut to different lengths?

Burunduk,

A cone may have calculable sizes along its length, however over all there is no single measurement that one is certain to make on a cone that will characterize the fit of that cone with a mating part. If there is slight barreling to the form of the cone then an infinite number of solutions can be generated to the question of cone angle. A best-fit cone will not reveal the "size" of the cone; it might reveal where the best-fit vertex is.

 

[dtmbiz]

3DDave
Yes right on queue you have recognized the example given for a cylindrical feature that is potentially produced as a conical feature would indeed have a cylindrical shaped Datum Feature Simulator.
My point is that same type Datum Feature Simulator with a conical shaped surface at MMC would expand as a cylindrical type simulator does to LMC (internal) within the tolerances specified.

If a conical surface has a prescribed cone angle and becomes a solid cone with a base diameter and a smaller diameter. That physically produced frustrum does have a physical size.

There can be e.g. two different tapered conical pins each having the same taper angle, with each having a different base diameter and different minor or smaller diameters each would result
in physically different sizes.

It seems as if you are approaching the definition for FOS when applied to conical features from a measurement / inspection perspective? Mathematics for theoretical cone ?

Produced conical shapes have imperfections just like any produced shape, thus the Similar Perfect Counterpart (or Datum Feature Simulator)

Greenimi
Tolerance of Location control is typically applied to an axis or center plane not a point derived from a circle. The tolerance can be applied as a boundary e.g. slot.
FOS has a definition which includes a datum axis, center plane, and center point in the case of a sphere. FOS are located to these datums. The tolerance zone is located about the datum
with exception of when the tolerance applies to a boundary. A conical feature by definition has a datum axis.

There is no "license" needed to be taken. Conical features, Linear Extruded features, and Complex features are clearly irregular Features of Size as defined with examples shown in 2009 ASME Y14.5.
There are many more companies than the one I unfortunately mentioned that recognize and teach the aforementioned features as irregular Features of Size including the "Machine Design" publication.

 

[greenimi]

Conical features, Linear Extruded features, and Complex features are clearly irregular Features of Size as defined with examples shown in 2009 ASME Y14.5.

Could you, please, provide evidence of your statement?
- examples, figures from 14.5-2009, 2018?
- examples (from other training companies) training materials?

In my understanding a FOS can be: regular or irregular. On both you can apply position.
IMHO, a cone is neither.
My supporting evidence: never seen an ASME example where position could be applied to a cone.
Did you?
If yes, please provide some good examples.

 

[greenimi]

https://www.eng-tips.com/viewthread.cfm?qid=439737

Above is another discussion on why a cone could not be IFOS (irregular feature of size):
Reasoning is the same: CANNOT contain or be contained by an AME
(same as pmarc's jpg from 14 Mar 19 18:23), meaning further contraction IS possible and no AME could be determined)

 

[dtmbiz]

Greenimi

Maybe you can tell me what you belive the purpose for adding the defintion of "irregular FOS", what is it intended to address. Please give examples of the shapes that are not covered within regular FOS.

Please explain the rationale for the datums that ASME Y14.5 demonstrates can be established in Fig 4-3 (posted earlier in this thread)from those type features shown.

If they are not FOS (irregular) then what it the point to demonstrate the datums within those shapes ?

What ASME Y14.5 terminology would you apply to the newly added definitions for Conical features, Linear Extruded features, and Complex features in respect to features?
Just a feature?

Why is there a subset classification for FOS in respect to any feature ? Any particular reason those type features (FOS) are used to simulate and establish theoretical datums ?

Geometrically an AME related or unrelated exists (per ASME Y14.5 definition of AME) for these type features that have been produced. Are you saying they cannot be physically defined envelopes ?

 

[3DDave]

The elements of the frustum can have a size. The cone cannot. (Queue is getting in line. Cue is, in this context, an initiator.)

A conical surface cannot expand or contract; it subtends an angle that is just cut off at different locations.

Irregular FOS was a patch to cover highly interrupted FOS cases and to force the terminology to also apply to non-FOS boundaries controlled by profile tolerances. They range from mildly interesting: such as Fig. 4-33, where the tangent points are considered as a group to establish a datum plane; Fig. 4-34 and Fig. 4-35, where the datum features are highly interrupted; to the inexplicable Fig. 8-24 hijack.

Notice the name of a feature changes when the geometric characteristic applied to it changes:

Fig. 8-19 Composite Profile Tolerancing of an Irregular Feature (not an FOS)
Fig. 8-20 Composite Profile Tolerancing of a Feature (not an FOS)
Fig. 8-24 MMC Principle Used With Profile Controls (only an FOS per a different section)

Only the last one, using a position tolerance, is promoted to IFOS, outside of the section on profile, by the team working on IFOS without apparent coordination with the Profile group in order to leverage Positional tolerance. Note the lack of mention of irregular features of size in the Tolerance of Location

Already mentioned - many shapes are not FOS and can be datum features. The cone has no characteristic size. How can it be a FOS without a characteristic size? This question is also for the ones who grabbed Fig. 8-24 and jammed FOS status down the throats of the Profile group.

The more I look the more I'm convinced the section 4 group was working alone.

 

[greenimi]

dtmbiz,

Maybe you can tell me what you belive the purpose for adding the defintion of "irregular FOS", what is it intended to address. Please give examples of the shapes that are not covered within regular FOS.

If you look (and I am sure you did) in the same training materials from AGI you will see pretty clearly what shapes are covered within regular FOS and which ones are covered by IFOS
Basically IFOS are, all the ones where the opposing and parallel elements could not be determined on each and every section (side note: and then consequently rule#1 is not applicable), but an AME could be found (IFOS are features or collection of features that may either contain or be contained by and actual envelope)

I am sure you know that.

A cone is neither and position on a cone could not be applied.

Fig4.3 shows examples of IFOS that could be used as a datum features. And, by the way, the cone is control with profile (and not position)

If they are not FOS (irregular) then what it the point to demonstrate the datums within those shapes ?

What ASME Y14.5 terminology would you apply to the newly added definitions for Conical features, Linear Extruded features, and Complex features in respect to features?
Just a feature?

I would say the answer is again in your training material (AGI): feature of "Non-size" or Surface features.

Geometrically an AME related or unrelated exists (per ASME Y14.5 definition of AME) for these type features that have been produced. Are you saying they cannot be physically defined envelopes ?

If an actual mating envelope could not be determined-repeatable and reproducible- (again, because the further contraction possible) then, probably, is not an IFOS and should be defined with profile.

Some other of your questions addressed to me were already answered by 3DDave, so I won't go over them again (as I might not have his level of knowledge and abilities to dissect the subject)


Out of my curiosity, and knowing you have a lengthy carrier, why you insist the cones are IFOS?

And since I answered mostly all of your questions (and you did not answer any of mine) could I ask again:

greenimi (Mechanical)
2 Dec 19 19:37
Quote (dtmbiz)
Conical features, Linear Extruded features, and Complex features are clearly irregular Features of Size as defined with examples shown in 2009 ASME Y14.5.

Could you, please, provide evidence of your statement?
- examples, figures from 14.5-2009, 2018?
- examples (from other training companies) training materials?

In my understanding a FOS can be: regular or irregular. On both you can apply position.
IMHO, a cone is neither.
My supporting evidence: never seen an ASME example where position could be applied to a cone.
Did you?
If yes, please provide some good examples.

I prefer you to answer now my questions, before you post other ones...I think that is the polite way for a conversation.....

 

[dtmbiz]

3DDave
I will reiterate this thread was intended to focus on an individual’s understanding for the “purpose of FOS and AME” IAW ASME Y14.5 (language, principles, definitions, graphic examples, definitions)
Thread is not intended to 'dismiss' anyone’s personal understanding.
Disagreements are inevitable. Debate regarding individual’s posts for their understanding is inevitable.
Consideration of an individual's understanding is valuable for considering the soundness of one's own understanding.

Even though I personally disagree with some of your posts from the standpoint of ASME Y14.5 2009
language and its” intent” according to my understanding (interpretation) I do appreciate your views.

The examples you have given do not address the intent for defining datums for Fig 4-3 and DOF constraints within those feature types. (emphasis on conical mainly in this thread)

The examples you have cited are for tolerances that apply to a profile’s boundary. Where the tolerance zone is not related to location about a datum.

Figure 8-19 contains an irregular shaped feature with a composite profile tolerance applied...

The above excerpt from the example's in your post does not reference a FOS (irregular) rather an "irregular shaped feature" (there is a substantial difference)

One primary FOS purpose is to simulate a datum to which a tolerance zone is applied. (excluding boundary exceptions)
The "irregular shaped feature" has the tolerance zone located about the profile shape not a datum.

conical surface cannot expand or contract; it subtends an angle that is just cut off at different locations.

I will take that to mean expand or contract in reference to it's "perfect" form and size. I certainly can introduce pressure to expand it to the point of "blowing up".
If you consider a cylinder (internal) e.g at MMC it also could not expand to LMC, beyond its MMC surface area and size to LMC larger surface area and size (larger radius).

I would agree with, any surface of revolution cannot expand or contract while keeping a specific perfect "size' and form without a change in surface area.
I do believe a "perfect form" (process tooling/ equipment perfect) can expand or contract to define the largest "perfect form of a feature" within an imperfectly produced feature"

One example of processing tooling might be an array of gage pins (angled in consideration of a conical feature) oriented about a common axis that would expand or contract a simulated “perfect form” that
would “straight line contact” with the “high points” of an imperfectly produced conical feature.
This could for practical purposes define the largest perfect form to fit within an imperfectly produced conical feature including the axis location and orientation.

My understanding of AME "similar perfect feature(s) counterpart" regarding expansion or contraction is to expand or contract the prescribed "perfect form" in order to contact the produced features high points establishing a “mating envelope”

 

[dtmbiz]

Greenimi,

Your non-answers include no reference to ASME Y14.5 2009 that would support your interpretations which again this thread is intended to focus on.
Your answers also assert that I have some sort of agreement with your answers in which I cannot find any agreement. Example:

If an actual mating envelope could not be determined-repeatable and reproducible- (again, because the further contraction possible) then, probably, is not an IFOS and should be defined with profile.

I have no idea of what you mean. It does not seem that you are aware that an AME is defined by each uniquely produced feature.
Where does the idea come from that an AME is required to be "repeatable and reproducible" ? That statement defies the definition of an AME.
No need to go further with the rest of my disagreements.

The reason that my post was a list of questions was to direct you to the intent of the OP, which
was for others to post their individual understanding for the “purpose of FOS & AME” specifically
based on ASME Y14.5 2009.

I do not see in the thread where you ever post your understanding for “purpose of FOS & AME” whether it is based on Y14.5 or not.

ASME Y14.5 2009 (this thread) is the evidence. An analogy may be where a traffic accident is the only available evidence for investigators to understand the why, how, and reason etc. for their conclusions. There is no further “evidence” for interpretation, only other interpretations that either support or don’t support an individual’s conclusion. The standard itself is the only available evidence to the general body of ‘users”.

Posts in this thread for the most part ignore or avoid the evidence in particularly of the previously posted Fig 4-3 which are examples of the theoretical type datums which can be defined within the additions of Conical features, Linear Extruded features, and Complex features.

Which leads back to the question for “purpose of FOS” that is being asked due to others in the forum rejection of conical features as FOS (irregular). I have been unable to find any other reputable ASME company or organization that does not accept and teach that Conical features in Y14.5 2009 are FOS (irregular). If you can find such a reputable company, organization or even university professor that is teaching otherwise, please let us know for further consideration.

The purpose of FOS is to establish by simulation those theoretical datums (axis, center plane, center point) via processing equipment.

In section 4-23 a conical feature is used as a primary datum. The DOFs are explained relative to apex and axis. Exactly what a FOS does, define theoretical type datums.
If it is not a FOS then what other Y14.5 2009 principle is this accomplished by?

 

[greenimi]

dtmbiz,

Not with the intent of dragging you into a lengthy discussion but for my own edification, could you at least point out what exactly is wrong with my assessment (of the cone not being IFOS) so I can look into it further myself?

 

[greenimi]

I have been unable to find any other reputable ASME company or organization that does not accept and teach that Conical features in Y14.5 2009 are FOS (irregular).

Could you, please explain this? Sure I am not understanding your statement.

 

[dtmbiz]

Greenimi

1) I cannot explain why a cone is not a IFOS other than to explain why it is an IFOS IAW (In Accordance With). I have done so thru numerous references to Y14.5 2009 in my posts.

There are other numerous posts that do not accept conical features as IFOS because they believe a cone isn’t contained or contained by an AME. I believe a cone does have an UAME and can have a RAME
when located and oriented to a DRF. Or not because a cone does not have size. (strongly disagree..see below)

An Actual Mating Envelope is simply any uniquely produced imperfect produced FOS's "envelope" including it's size & form (UAME). That envelope is defined by a similar perfect counterpart (inverse part, i.e. male vs. female) which is simulated by processing equipment. The envelope is also limited to the size limits of the feature (tolerances). It simulates what is the maximum size "perfect mating" counterpart will fit within that envelope.

E.g. if conical feature is produced toward the LMC and has a slight bend to the axis which us determined from its form, what size similar perfect counterpart can still fit into that specific hole.
Why define an AME ? One reason is to technically explain the potential amount of datum shift /displacement in general terms. The specific mating male and female features would need to be measured in
order to determine the actual datum shift /displacement available if there is any.

There are in theory no two AME's exactly alike that produce the exact same AME. Calculations do not define an AME, measurements of a specifically produced feature do.
An AME is a simple relative comparison of geometry. One comparable is the imperfect hole and the other a "perfect" counterpart.

2) The argument that a cone doesn’t have size is not true for my definition of a cone nor mathematical definitions of a cone.
A cone has base value for diameter, it has a height, and taper angle or smaller diameter if the apex is not included in the feature. It also has an axis.
I wonder how those who argue a cone does not have size, calculate area or volume for a prescribed cone ? Answer is: not possible.

3) There is no Engineering publication, ASME Y14.5 recognized "training" company, or subject matter authority that teaches that a cone is not a IFOS (that I can find)
All that I have been able to find do teach conical features to be an IFOS.
If there is such an entity, please let us know.

 

[3DDave]

A cone only has a base value because it is truncated - it is the truncation that has the size, not the cone.

Change the truncation and nothing else and the cone still fits just as tightly to a mating conical feature.
Bore out a hole and the mating bolt rattles more.

(Random bolding because why not?)

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.

As much effort has gone into deriving this, it seems that a single document with specific Y14.5 references and explanations about the inferences along with examples of training materials where IFOS and cone appear, referring to the same feature, would better support the position rather than picking at bits of it across dozens of posts.