Dual Flatness callouts on ISO GPS

SeasonLee · Oct 30, 2020

Please ref to the section view below:

Its an ISO spec, I havn't seen dual flatness callouts before, what is the meaning of each callout?
Thanks for the help.

Season

Burunduk · Oct 30, 2020

Looks like the larger flatness tolerance callout is specified with the circled F modifier which I think means the same thing as in ASME - the requirement is for the free state condition. That suggests that the smaller flatness tolerance is for the restrained condition.

SeasonLee · Oct 30, 2020

Thanks, Burunduk.

For the Free State modifier, are there any differences between ASME GD&T and ISO GPS?

Season

greenimi · Oct 30, 2020

I just know that ISO 10579 is the ISO standard which defines free state modifier.
I don't think there is a big difference between ASME and ISO on this aspect, maybe just some subtle differences which I am not aware about.

SeasonLee · Oct 30, 2020

Just checked the ISO standard, according to the examples from ISO 10579 Annex A (shown below), it seems some errors on my first posted figure, the dual flatness callouts with individual flatness symbol while the example on ISO standard sharing a single flatness symbol. A lot I need to know and learn from GPS.

Season

cr7 · Oct 30, 2020

SeasonLee said:
Just checked the ISO standard, according to the examples from ISO 10579 Annex A (shown below), it seems some errors on my first posted figure, the dual flatness callouts with individual flatness symbol while the example on ISO standard sharing a single flatness symbol. A lot I need to know and learn from GPS.

It's not a mistake, it can be used both ways.

Single symbol can be used also on Position or Profile tolerance for example, but then the reader should be extra careful to which standard is it. If ASME that would be a composite, ISO doesn't have composite callouts.
So in ISO is the same if there is a single symbol or multiple.

SeasonLee · Oct 30, 2020

cr7 said:
It's not a mistake, it can be used both ways.

Thanks for your information, may I ask any documents to support it.

Season

cr7 · Oct 30, 2020

SeasonLee, I only have 1 source in front of me that I can refer to and that's Robert Roithmeier, 2016, Inspection-oriented Tolerancing - Size, Form and Location, page 109
Probably not very helpful, I know, I hope someone can refer to actual paragraphs in GPS.

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Dual Flatness callouts on ISO GPS

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