Relationship of Rule 1 with perpendicularity tolerance

[AM Engineer]

Hello all.

Please find the hand drawn drawing of a rectangular plate.

The bottom surface is datum feature A. The perpendicularity call out for secondary datum feature is given. Value is not specified intentionaly.

The question is

" As per Rule 1, the length dimension of 9.8-10.2 can be banana like. Having a form error of 0.4 simultaneously on both surfaces. Does this error has anything to do with perpendicularity with respect to datum feature simulator A".

Thank you in advance.

 

[3DDave]

Nevermind. I should have known better.

 

[Belanger]

Does this error [have] anything to do with perpendicularity with respect to datum feature simulator A?

Yes, it does have something to do with the perpendicularity callout, in that it will cause the perp to fail.
Add a circled T into the perpendicularity FCF and then the answer would be no.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

It's just my guess, but I think that AM_Engineer is asking whether there is a relationship between the perpendicularity tolerance value and the size tolerance or not. If that guess is correct, the answer is no, there is no such relationship.

 

[drawoh]

AM Engineer,

You show a width dimension and tolerance, but not a height. Is rule[ ]1 meaningful without a height? If form is perfect at MMC/B, would that not control perpendicularity?

--
JHG

 

[AM Engineer]

Belanger

Isnt the automatic indirect perp control there coming from size tolerance??

 

[AM Engineer]

Pmarc

Thanx for commenting sir.

Yes. I meant exactly what you said.

But still im confused.

There is no relationship between size limits and perp, i interpret this statement as that rectangular plate could be a parallelogram because size does not conrrol perpendicularity in this case.

However, what about if 0.4 form error is there in worst case. As Belanger said we will reject this part based upon nonconformed perp, so if i have to conform the perp to less than 0 4 then i need to refine it?

This is so confusing.

Please correct and advice whenever free.

Best Regards

WQS

 

[pmarc]

In absence of a perpendicularity tolerance, the part can be any parallelogram because by definition (see para. 2.7.4 in Y14.5-2009) Rule #1 does not control orientation of the 9.8-10.2 feature relative to any other feature. If the feature is produced at 10.2 everywhere, it can still be at any angle relative to the datum plane established from the datum feature A.

If there is a perpendicularity tolerance specified and its value is less than the size tolerance, for example 0.1, the part can be a parallelogram angle between the left wall and the datum plane A is controlled within 0.1. But this also means that flatness error of the left wall of the 9.8-10.2 width is indirectly controlled within 0.1. In other words, that wall cannot have measured flatness error of 0.4 because this would never conform to the specified perpendicularity requirement of 0.1.

If there is a perpendicularity tolerance specified and its value is greater than the size tolerance, for example 2.0, the part can be a parallelogram angle between the left wall and the datum plane A is controlled within 2.0. In that case, flatness error of the left wall of the 9.8-10.2 width is indirectly controlled by the size tolerance, that is within 0.4. In other words, that wall can have measured flatness error of 0.4 because this doesn't conflict with the specified perpendicularity requirement of 2.0.

 

[Belanger]

pmarc and AM Engineer -- I think my original post summarized the same thing.
If the original question was "asking whether there is a relationship between the perpendicularity tolerance value and the size tolerance or not" (as posted above), then the answer is indeed YES. This is only because the perpendicularity tolerance must be less than the size tolerance; thus, there is a relationship!

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

J-P,
What I have been trying to say is actually quite the opposite. In cases like the one shown on OP's sketch there in NO relationship (dependency) between the size tolerance value and the perpendicularity tolerance value. Which means that for the defined size tolerance of 0.4, the defined perpendicularity tolerance can be of any value - 0.1 or 2.0 or even greater than 2.0.

 

[AM Engineer]

Hello pmarc.

You mentioned in your 2nd post that orientation of left wall is not controlled by Rule 1 relative to any feature.

It means orientation is entirely uncontrolled??

Also, you editted your post and i saw two words " any parallelogram".

Please find attached hand drawn drawing. Sorry for my poor drawing.

Is this you mean by any parallelogram??

 

[aniiben]

pmarc (Mechanical)17 Apr 12 16:14

https://www.eng-tips.com/viewthread.cfm?qid=320126

AM Engineer,

I found this discussion. See the above post from pmarc

 

[aniiben]

And one more "perpendicularity" (searched for "maximum perpendicularity") discussion....which I am still digesting myself.

https://www.eng-tips.com/viewthread.cfm?qid=319066

 

[Belanger]

pmarc -- But that's not what the OP was asking. The OP was specifically asking about a part that used up that size tolerance with pure form error (the "banana" shape). Certainly the perpendicularity tolerance can itself be anything, but in the case presented to us, the perpendicularity tolerance will fail.

The missing link that connects the two concepts is form (flatness). I would certainly agree with you if it were not curved but merely a straight-sided parallelogram. But I was merely going with the question as it was posed. Sorry for any confusion.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[pmarc]

J-P,
In the case presented to us, there is no way that the perpendicularity tolerance will ever fail because its value is '?'.

This '?' is what made me think that the OP was actually asking if '?' could be any number or just a number less than the size tolerance value (0.4 in this case).

I hope you agree with the statement that '?' can be any number regardless of how the actual geometry of the part looks like.

I too apologize for any confusion created here.

 

[AM Engineer]

I understood the concept.

Part can be any parallelogram while also being banana. In worst case, 0.4 form error will be there and angle could be of any value. Lesser or more than size tolerance.

 

[AM Engineer]

Thanx pmarc and belanger and all who responded.
Just one last question.

In case perp tolerance is greater than size tolerance, lets say 2 mm, then flaatness of that considered surface is controlled within 0.4, not 2

Does this means that the statement in the standard " Orientation control applied to surfaces also control flatness upto the extent of orientation tolerance " is not absolutely true??

Thank you in advance.

 

[greenimi]

AM Engineer,

I guess a more pertinent statement from Y14.5 is:
"When specifying a form tolerance, consideration must be given to the control of form already established through other tolerances such as size (Rule #1), orientation, runout, and profile controls."

Also, could you please provide more details on why you think that your posted statement is not true?

In case perp tolerance is greater than size tolerance, lets say 2 mm, then flaatness of that considered surface is controlled within 0.4, not 2

Does this means that the statement in the standard " Orientation control applied to surfaces also control flatness upto the extent of orientation tolerance " is not absolutely true??

 

[AM Engineer]

Greenimi

What i meant was this.

Read the following statement from the standard.

"an orientation tolerance, when applied to a plane surface, controls flatness to the extent of the orientation tolerance" .

As discussed before, if the perpendicularity tolerance is greater than size tolerance then the flatness of considered surface is controlled within size tolerance, not perpendicularity tolerance.

So, there is a confusion that how we should interpret the wording of standard that flatness is controlled to the EXTENT OF ORIENTATION TOLERANCE?

 

[greenimi]

standard that flatness is controlled to the EXTENT OF ORIENTATION TOLERANCE

So, yes, the flatness is controlled by the extent of the orientation....meaning cannot be bigger than the orientation tolerance (in your case 2mm)

But, there maybe other callouts on the same drawing that limit the flatness and in your case looks like the size will do just that (limits the flatness)---see my posted statement from Y14.5 : ""When specifying a form tolerance, consideration must be given to the control of form already established through other tolerances such as size (Rule #1), orientation, runout, and profile controls." "