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Rule1 not required

Rule1 not required

RE: Rule1 not required

aniiben,

Your sides would be perpendicular to within 1° as per your note. Your maximum size would be 38.2mm plus 46.2mm×sin(1°).

--
JHG

RE: Rule1 not required

The maximum envelope would seem to be 38.4 mm -- this comes from the maximum local size of 38.2 plus the form error of 0.2 on the datum feature.
The minimum envelope would be 37.6 mm, derived in a similar way. (We usually don't speak about a minimum mating envelope for an external feature of size, but it makes for a good discussion question here).

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

RE: Rule1 not required

I assume the question is not intended to take in consideration the default angle tolerances, but only shown geometrical callouts- flatness and parallelism.

RE: Rule1 not required

greenimi,

I am assuming that angle tolerances matter. Rule #1 controls this.

--
JHG

RE: Rule1 not required

Hi drawoh -- the corner angles have nothing to do with the question. And Rule #1 has nothing to do with angle tolerances.
The OP asked about the envelope of the 38 mm width dimension. Using terminology from Y14.5, it's a question about the unrelated actual mating envelope (UAME) rather than the related actual mating envelope (RAME).

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

RE: Rule1 not required

I agree with J-P that rule 1 (or the lack thereof) has nothing to do with the angle tolerances. I suspect the angle tolerances applies with the now "infamous" unless otherwise specified.

RE: Rule1 not required

J-P:

Sorry coming late to this thread. I was off for a long weekend.

I wrestle with the interrelationship between size and form when independency "I" is applied - is assume "I" is equal to "PERFECT FORM AT MMC NOT REQUIRED" . So, given your 38.4 value, which includes the flatness on Datum C, why did you ignore the parallelism with implied flatness on the other side?

Certified Sr. GD&T Professional

RE: Rule1 not required

Mkscski -- I've created a hand sketch to show how I look at it (see attached). I didn't include the parallelism tolerance because I was assuming that the part is already at its maximum local size. If the right-hand surface of my sketch curved the other way (and made the parallelism additive), then it would fail the actual local size requirement.

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

RE: Rule1 not required

J-P:

Thanks. This was what I was thinking too. I am pretty sure ISO allows the GDT tol to be additive to the size when "I" is applied. And I assumed the Y14.5 did NOT have this interpretation.

Certified Sr. GD&T Professional

RE: Rule1 not required

mkcski,
Could you, please, expand a little bit on how the ISO allows GDT to be additive and how the ASME (with "I" applied) doesn't?
I am trying to grasp the differences between these two concepts (ISO vs ASME) on an seemingly equivalent schemes.

Thank you
Gab

RE: Rule1 not required

gabimot:

Give me a day or two to dig out and scan my ISO ref material - Alex Krulikowskis' "ISO Geometrical Tolerancing" guide pages 51 and 137, 144 if you have a copy.

Certified Sr. GD&T Professional

RE: Rule1 not required

Thank you mkcski. You have the entire week... if you wish.
And will be a Christmas gift!
P.S. I do not have much ISO material (except this forum)and the www/google search.

RE: Rule1 not required

gabinot:

Your welcome.

Certified Sr. GD&T Professional

RE: Rule1 not required

Thank you mkcski,
I will study (try to understand) your provided material and follow-up with additional questions (most likely) about the differences between ISO (default / Independency) and ASME ("forced" Independency I)

RE: Rule1 not required

gabimot:

This topic is not one I have studied and examined in detail. Maybe you want to start another "independency" post.

Certified Sr. GD&T Professional

RE: Rule1 not required

Let me try and I am sure if I will miss something or provide wrong information there are people/experts here who will set the record straight.

I do not know if ISO (with Independency principle, ISO 8015 stated) and ASME (with I symbol attached to 38±0.2 dimension) will have different extreme boundaries (OP question has been: what would be the maximum and minimum envelope that 38±0.2 dimension would never violate?)

In my opinion would be the same for both envelopes or extreme boundaries (38.4 and 37.6) Please, correct me if I am wrong. I am trying to learn from each and every discussion.

Also, the parallelism would not be added to the sum of flatness and maximum material size. I am not sure how can I explain why (would not be added), but I would say because the orientation (parallelism in our case) never locates only orients and the extreme boundaries are already determined by the flatness and the size tolerance. Am I correct? Any orientation error should only be toward the inside of the material in order to not be exceeding the limits of size.

What I know is: The tolerance zone is limited by two parallel planes a distance 0.2 apart and parallel to the datum plane C. The extracted (actual) surface shall be contained between two parallel planes 0,2 apart, which are parallel to datum plane C.

Hmm, any errors in my statements? Or better to ask any truth?

RE: Rule1 not required

With ISO 8015 the linear measurements are all 2 opposing point measurements so the part could look like a banana or a wavy cut potato chip and still pass as long as every opposing point pair is within the tolerance. There really is no upper maximum on the envelope. ISO 8015 wants you to explicitly state each and every GD&T requirement rather than falling back on the envelope "crutch". I hate it.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Rule1 not required

greenimi:

Look at the attachment J-P on 12 Dec 17. This clarifies the ASME boundaries very well. The ISO analysis is more expansive because "I" is the default. I am not up to snuff as to how the GDT tolerances interact with the size.

Certified Sr. GD&T Professional

RE: Rule1 not required

dgallup:

I think hate is to soft of a word. We need more powerful 4-letter words. hahaha.

Certified Sr. GD&T Professional

RE: Rule1 not required

If we eliminate the "emotional effect of ISO 8015"bigsmile what would then be the "correct" answers for the OP questions in ISO and also in ASME? santa

RE: Rule1 not required

I do not have a copy of 8015 to review.

Certified Sr. GD&T Professional

RE: Rule1 not required

Greenimi -- I believe that everything you wrote in your earlier email today (the longer, earlier one) is correct. If ISO is used (with the 8015 independency assumption) or if ASME is used with the circled I, then the answers would be the same for all of these questions.

And your explanation for why parallelism isn't a factor sounds good, in my opinion.

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

RE: Rule1 not required

Quote (greenimi)

I am not sure how can I explain why (would not be added), but I would say because the orientation (parallelism in our case) never locates only orients and the extreme boundaries are already determined by the flatness and the size tolerance. Am I correct?

It's not that parallelism never matters. It's the relative size of the parallelism and flatness tolerances. Consider what would happen if the parallelism tolerance was very small.

RE: Rule1 not required

Nescius,
Well now I am confused. Why the relative size of the parallelism and flatness matters? Parallelism is for one side and flatness for the opposite one (which is the datum feature).
Not sure I understand how the provided answers will change if parallelism would be for example 0.01 instead of currently shown value of 0.2?

Could you please explain? Is your case/scenario affecting both ISO and ASME or just one of them?

Thanks

RE: Rule1 not required

In the sketch that John-Paul posted, imagine if the right edge was very flat/parallel. If the local size were to remain at 38.2 across the middle of the part, it would fail the local size requirement at the top and bottom.

I have no experience with ISO tolerancing, but I don't perceive any difference from ASME when it comes to the original question of this thread.

I have a question for the ISO folks. Is there an ISO standard that gives a rigorous definition of "local size" or "2 point measurement"?

RE: Rule1 not required

Quote (Nescius)

Is there an ISO standard that gives a rigorous definition of "local size" or "2 point measurement"?

ISO 14405-1:2016

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

RE: Rule1 not required

Quote (CheckerHater)

ISO 14405-1:2016

Thanks, CheckerHater.

RE: Rule1 not required

After I spent some time yesterday and go over the material posted by mkcski from ISO (Alex K) my understanding is that ISO and ASME differs on how the maximum and minimum envelopes are calculated.




ASME :as shown by J-P Belanger: 38.4 maximum envelope and 37.6 minimum envelope.

ISO: I would add/remove 0.2 for parallelism (from J-P Belanger) calculated values and consequently the values will be 38.6 for maximum and 37.4 for minimum.

Reason: I would say that the two tolerances (flatness and parallelism) cannot see each other due to the Independency principles. Alex K book states also: size and orientation are independent requirements and affect (or define) the extreme boundary of the feature of size.

Mkcski,

That concept you had in mind when you said:” I am pretty sure ISO allows the GDT tol to be additive to the size when "I" is applied. And I assumed the Y14.5 did NOT have this interpretation” ?

RE: Rule1 not required

gabimot -- If we say that ISO allows the max envelope to be 38.6, is it possible to meet the still-required max local size of 38.2?

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

RE: Rule1 not required

gabomit:

I made the distinction b/w ISO and ASME because unlike ASME, "I" is the default in ISO. From my understanding, when independency is in effect, the interpretation is the same for ASME and ISO.

Certified Sr. GD&T Professional

RE: Rule1 not required

Quote (Belanger)

gabimot -- If we say that ISO allows the max envelope to be 38.6, is it possible to meet the still-required max local size of 38.2

Hmm...ISO stuff..... Good question: I was thinking about it a little bit before, but maybe I am not thinking this correctly.
Follow me:
Actual local sizes are all at 38.2--perfect tab or rectangle, but bend--
For the orientation/parallelism we need the extracted median line to be within 0.2 (and not the entire surface of the opposite face of datum feature C). Now, I know the surface will control the median line but not vice-versa, so I concluded (maybe wrongfullybigears) the parallelism is additive....ponder...when the OP envelopes (maximum and minimum) "non-violation" condition.


RE: Rule1 not required

According to the graphic given in the first post, the GD&T is all surface stuff, so there is no median line to be considered. You are probably thinking of a "feature of size" geometric tolerance.

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

RE: Rule1 not required

Quote (Belanger)

According to the graphic given in the first post, the GD&T is all surface stuff, so there is no median line to be considered. You are probably thinking of a "feature of size" geometric tolerance.

Okay. So, If the OP case would be a cylinder and not a rectangle then your answer (38.2/ 37.2) will be different in ISO versus ASME? (since it is a rectangle the answer is the same)


RE: Rule1 not required

I guess if the part is a cylinder then no parallelism to be applied

RE: Rule1 not required

I assume, based on what we have discussed so far, we have concluded that 38.4 (maximum) and 37.6 (minimum) are the envelopes / answers for the OP questions on both systems: ISO GPS and ASME.

Now, I am challenging myself to find a case or cases where these two envelopes (maximum and minimum envelopes that a particular feature of size dimensions would never violate) are NOT the same in both systems (ISO GPS and ASME). I am just getting my feet wet in the ISO system (so to speak) therefore, sometimes I might not be on the right track.

Any good examples, of those kind of differences, would be greatly appreciated---just to “keep my brain alive” during the Holidays.

RE: Rule1 not required

greenimi:

From my understanding I wouldn't waste my time chasing differences in this area.

In general -in most cases differences between ASME and ISO don't exist. Hey...parts are physical and the geomantic characteristics of part features are the same no matter if they are defined in accordance with ASME or ISO standards. It just that the symbology to communicate the characteristics is different. Its like reading a foreign language. You need an interpreter to convert it to so you understand OR you learn how to read both and do the conversion in you head. In the end, the "words" (symbols) are different but the meaning is the same.

Certified Sr. GD&T Professional

RE: Rule1 not required

There would be different answers between the two systems if one (and only one) of these two things happened:

1) In the ASME example that the OP proposed, his extra note is removed

2) If the OP's note is retained in the ASME example, but the ISO example added a circled E for that width dimension

Then you'd be comparing an example of envelope-contained-by-size with an example of independency.

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

RE: Rule1 not required

I am wondering if there are ANY cases where the parallelism gets added to the form control and MMS in order to obtain the maximum envelope and how those cases would look like?
Cylinders/rectangular forms/ random shape

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