How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
(OP)
I have a rectangular block, with the width of 100+/-1 mm and one side face of the block is datum A
and the opposite face I have an tolerance frame that indicate parallelism with A within 0.2.
The question is which is the biggest width of the block 101,2 or 101?
Could anyone make reference to a standard?





RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
You need to tell us what drawing/GD&T standard you are working to (ASME, ISO other...) and if the envelope principle is in force.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
This has been discussed over in forum1103: Drafting Standards, GD&T & Tolerance Analysis but I'm having trouble finding a simple example/answer for you.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I would say 101.2 including the parallel tolerance.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I had the same opinion with you till few weeks ago when I started to play with CETOL6σ and
I saw that the parallelism is not consider for calculation of block width.
And I start to think that this might be true (CETOL6 σ approach)
because if the maximum width of the block would be 101,2 than the condition 100+/-1 would not be respected any more.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
Funny just after I posted I thought the same thing, similarly the same would apply for the minimum size too.
Theredfore the only conclusion can be the parallelism as to fall within the 99 to 101 dimension which seems reasonable.
desertfox
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
If envelope principle is invoked (default condition in ASME Y14.5 but not ISO) then the 'form' variation of the parallelism has to be within the size tolerance.
If this principle is not invoked than as I understand it the separate form tolerance becomes cumulative with the size tolerance but I'd be lying If I said I was 100% confident which is why I suggested that other forum.
I believe ISO 8015 is the relevant spec - a quick Google found an older copy of dubious copyright so I won't post a link but did crib this text:
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
Thanks for that, I will have a look at the ISO standard and post later
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I can't find anything about the envelope clause, it might help if the OP can confirm which ISO standard, I have access to ISO 1101
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
KENAT is referring to ISO 8015 from 1985,
but this is obsolete and replaced with a new version from 2011.
Any how the bought standards are saying the same think regarding independence principle.
I have a look over this standard/independence principle and, this makes me believe that the answer to my question is 151.2.
But I am not sure about this, and seem not logic, an additional constrain (parallelism) instead of reducing variation of the part is increasing this.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
"I have a look over this standard/independence principle and, this makes me believe that the answer to my question is 151.2." what is 151.2 I cannot find it.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I don't know if in reality in worst case the part look like in case one or two?
Based on the discustion that we had I am 90% that the corect worst case is two so the dimension of part is 151,2.
I consider this beeing important, imagine that you have a stack of 3 rectangular part (like in attachement) side by side
and you want to check the total width of your assembly.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I see now what 151.2 I thought it was a clause in the spec you were looking at.
Bottom line is, does the 151.2 dimension prevent assembly or function? if not I would live with it.
If it does interfere with assembly or function alter either the dimension or the parallel tolerance to suit your needs.
For the record I've always interpreted the tolerance's as we first discussed.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I think this answers your question:-
5.5 Independency principle
By default, every GPS specification for a feature or relation between features shall be fulfilled independent of
other specifications except when it is stated in a standard or by special indication (e.g. Ⓜ modifiers according
to ISO 2692, CZ according to ISO 1101 or Ⓔ modifiers according to ISO 14405-1) as part of the actual
specification.
You can find this on page 4 of ISO 8015 2011, so unless the symbol E in a circle is found our initial interpretation was correct.
RE: How to interpret GD&T into tolerance stuck-up analyze base on ISO standard?
I faked my own rectangular piece with different dimensions and large tolerances for clarity: