Flatness question 3

[SeasonLee]

A simple question arose while I was reading a textbook from Alex, please see the attached for the question, anything I missed? Thanks for the help.

Season

 

[pmarc]

Season,
Out of curiosity, what is the answer for flatness callout labeled "C"?

 

[SeasonLee]

Labeled "C" is not on the application problems, so no answer.

Season

 

[CheckerHater]

The flatness requirement "G" being applied to extension line overrides "perfect form at MMC" requirement.

The part now may fit 12.5 boundary (see 14.5-2009 Fig.5-8)

 

[pmarc]

Season,
I asked for "C" because according to this drawing - since the chamfer B is not dimensioned at all - the C can be of any value. I wanted to know if the answer sheet confirms this logic or not.

Similar thinking may be applied to "D" callout. The drawing does not control size of upper part of the width. Notice that there is no CF modifier next to 12+/-0.2 dimension, so as a matter of fact this dimension does not apply to the upper part of the width, thus the "D" flatness tolerance can be of any value.

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The flatness requirement "G" being applied to extension line overrides "perfect form at MMC" requirement.

The part now may fit 12.5 boundary (see 14.5-2009 Fig.5-8)

Wow! That is really interesting theory, CH.

 

[CheckerHater]

We are talking about flatness of the median, right?

Posting from work is getting harder

 

[pmarc]

No, we are not talking about flatness of the median. It is a flatness callout applied to a surface.

 

[CheckerHater]

I mean "G" is applied to median.

It frees "D" to be up to 0.5

 

[pmarc]

"G" is not applied to median plane. It is applied to surface "F", so actually it does not override "perfect form at MMC" rule.

 

[3DDave]

It looks like it is either a typo or a 'spot the error' example.

 

[SeasonLee]

pmarc, you are right.

I didn't notice the notch, if CF modifier added next to dim 12±0.2, then the interrupted surface will be treated as a single surface, in this case the Labeled "D" is not standard-compliant, am I right?

Season

 

[pmarc]

Yes, if CF is added to 12±0.2 dimension, the callout "D" will not be standard-compliant.

 

[SeasonLee]

pmarc, One more question:

so as a matter of fact this dimension does not apply to the upper part of the width, thus the "D" flatness tolerance can be of any value.

Why the answer sheet on upper part (labeled "I") the maximum flatness deviation allowed is 0.4?

Season

 

[pmarc]

I have no idea, Season.
If the answer sheet says that maximum flatness error of surface "I" is 0.4, I don't see how flatness tolerance "D" can be standard-compliant.

Can you show entire exercise together with the answers?

 

[SeasonLee]

Here is the question and answer sheet(chapter 9).
Thanks

Season

 

[pmarc]

The attachment is not working.

 

[3DDave]

Don't use the & in the file name for the attachment.

 

[CheckerHater]

"G" is not applied to median plane. It is applied to surface "F", so actually it does not override "perfect form at MMC" rule.

Insulting me will not make you right.

For the beginning, yes, indeed, FCF applied to dimension extension line overrides Rule 1

It's not a "theory", it's a fact. It is not someone else interpretation, it is in black and white in standard book.

Will be back with more.

 

[SeasonLee]

Upload again, please see chapter 9 answer sheet. The problem seems come from the file name with "&", had changed the file name from "Flatness Q&A" to "Flatness Q and A".

Season

 

[CheckerHater]

Wow, that's even more interesting!