Rule1 not required
Rule1 not required
(OP)
ASME Y14.5-2009
If drawing has a general note "PERFECT FORM AT MMC NOT REQUIRED" what would be the maximum and minimum envelope that 38±0.2 dimension would never violate?
If drawing has a general note "PERFECT FORM AT MMC NOT REQUIRED" what would be the maximum and minimum envelope that 38±0.2 dimension would never violate?





RE: Rule1 not required
Your sides would be perpendicular to within 1° as per your note. Your maximum size would be 38.2mm plus 46.2mm×sin(1°).
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JHG
RE: Rule1 not required
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
RE: Rule1 not required
I am assuming that angle tolerances matter. Rule #1 controls this.
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JHG
RE: Rule1 not required
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
RE: Rule1 not required
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
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Rule1 not required
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
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
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
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
Your welcome.
Certified Sr. GD&T Professional
RE: Rule1 not required
Here ya go. See attached.
Certified Sr. GD&T Professional
RE: Rule1 not required
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
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
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
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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
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
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
RE: Rule1 not required
Certified Sr. GD&T Professional
RE: Rule1 not required
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
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
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
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
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
Thanks, CheckerHater.
RE: Rule1 not required
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
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Rule1 not required
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
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 wrongfully
RE: Rule1 not required
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Rule1 not required
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
RE: Rule1 not required
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
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
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
Cylinders/rectangular forms/ random shape