ISO Flatness per Unit area? 2

[SeasonLee]

Please ref to Sec A-A, Flatness|0.2/50
Is it a flatness per unit area callout? flatness is allowed to apply on a unit basis in ASME Y14.5, how about ISO?
Is 50 an area of 50 X 50 square or Ø50 circle?

Thanks for all of your comments

SeasonLee

 

[pmarc]

flatness is allowed to apply on a unit basis in ASME Y14.5, how about ISO?

Though I could not find a specific example, I do not think there is anything in ISO standards that would forbid application of flatness per unit area callout.

Is 50 an area of 50 X 50 square or Ø50 circle?

In my opinion this is not clear. My best guess would be that instead of controlling flatness of the surface for whole height of the part (reference dimension 222.41) someone wants to refine the area to height=50 and because the surface does not have fixed dimension in orthogonal direction there is lack of second value clearly defining per unit area in flatness FCF.

 

[CheckerHater]

Older version of ISO 1101 clearly says “restricted length”, like “restricted area” is out of question.
There is 2012 version out there, but I didn’t have a chance to see it.
Didn’t make it any more clear, did I?

 

[pmarc]

The very same example and text is in 2012 version of ISO 1101.
I guess we do not want to start the discussion about extension of principles again, do we, CH?

 

[CheckerHater]

As long as we stay away from tangency

 

[SeasonLee]

Thanks for the help, CH and pmarc.

SeasonLee

 

[dgallup]

Not saying this is an authority, but My CAD software (supposedly configured to ISO standards) will let me make a flatness per unit area. The choices for the unit area can be d x d, diameter d or a "square symbol" d. So none of those match the OP's symbol. But it must be a unit of area for flatness, not unit of length like straightness.

Having said that, my copy of ISO 1101-1983 shows an example of parallelism per unit length. It says that the value applies to all lines of the restricted length in any position and any direction. I would think the same should apply to flatness since is is quite similar to parallelism without a datum reference. This does match the OP's symbol.

So I think it means 0.2 mm of flatness in any 50 mm length in any position and direction on the indicated surface.

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[JMarv]

parallelism per unit length

Joe
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[SeasonLee]

dgallup, thanks for your comments.

I can't find out what you mentioned on ISO 1101-2004,would you mind to post a snapshot. BTW,there is always a datum reference on parallelism.

SeasonLee

 

[dgallup]

Yes, parallelism has to have a datum. But is you take this parallelism example and extend it to flatness it would explain your drawing symbol. And Joe, I agree that parallelism or flatness per unit length does not make as much sense as per unit area. I did not write the ISO spec, just reporting what I found.

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[SeasonLee]

Thanks lot,dgallup.

SeasonLee

 

[SeasonLee]

dgallup, your post makes me think about the differences between ASME and ISO, the restrictive tolerance is only allowed for geometrical tolerance without datum reference in ASME Y14.5, but it allowed for geometrical tolerance with datum reference in ISO. Thanks again

SeasonLee

 

[pmarc]

the restrictive tolerance is only allowed for geometrical tolerance without datum reference in ASME Y14.5

I would not say that. We had a debate about it not so long ago.

http://www.eng-tips.com/viewthread.cfm?qid=327653