free state 1

[cervantes]

Hi

there is only one example in ASME standard and it is also hard to find anything else in the net.

There is a small plate of aluminium 3x15 which bends under its own weight or it is just naturally bended due to material physics.

It will be attached later to flat surface so it will be straight anyway.

But to clarify the drawings and reduce number of quality reports - can I use free state for straightness like presented on the drawing?

I meant - in free state, straightness of profile can be between 5 mm's.

Any other tips? Is this one is ok?

Thanks

 

[CheckerHater]

Yes, using Free state modifier implies that your part is flexible and special considerations are required.

You may also specify tolerances in restrained state and HOW exactly you want part to be restrained for inspection. (Usually simulating assembly)

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cervantes]

thanks, but do you have any objections with regards to my rough drawing proposal?

 

[CheckerHater]

The drawing really is "rough", so it's hard to tell.

The (F) symbol should be next to tolerance value and not in its own compartment.

Also, depending on what are you actually measure, you may want to specify flatness rather than straightness.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cervantes]

1) I prepared better drawing
2) Yes, I know, I made a mistake, F is now next to tolerance
3) It can be flatness for this case, we can take whole surface under consideration, not only single line of profile

So - this one would be now fully correct?

 

[Belanger]

But recall that Rule #1 automatically goes away for a non-rigid part. So one could argue that the F modifier isn't necessary here.

I've only used F when a part is restrained per a general note yet I want one particular feature control frame to be checked in the unrestrained condition.

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

 

[CheckerHater]

More like this.

I would accept it, but you may see different opinions.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[cervantes]

thanks all

Belanger: I am an European, we do not have envelope requirement as a default option

 

[CheckerHater]

But recall that Rule #1 automatically goes away for a non-rigid part. So one could argue that the F modifier isn't necessary here.

But how do you know that part is actually flexible?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

Cervantes -- sorry I hadn't realized that the discussion pertained to ISO.

CH -- (back to ASME for a moment) -- is it true then that a non-rigid part must either have the free-state modifier or else have a restraining note?

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

 

[greenimi]

J-P,
Re:" is it true then that a non-rigid part must either have the free-state modifier or else have a restraining note?"

What about having only AVG note near the size dimension? Does it make it flexible?

 

[Belanger]

Green, that's not my concern right now ... let me wait on that one. The question is whether Y14.5 requires tolerances for a non-rigid part to be given the F modifier, or tagged with a restraint note, or neither is required?

Not a trick question -- I'm honestly asking how folks interpret para. 2.7.2(b) and 5.5-5.5.2.

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

 

[CheckerHater]

@Belanger:

Here is one of possible interpretations from James D. Meadows' book. Frames with and without (F) symbol have different meaning. Restrained control requires note on the drawing.



"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

Thanks (really) but I disagree: Frames with and without F actually do have the same meaning.
Paragraph 4.20 clearly states that "all tolerances apply in a free-state condition." So the F symbol is not needed, even on flexible parts! The only reason F would make sense is to provide a specific FCF with an escape clause from a general restraint note (see para. 5.5.1).
I think that's the point of Meadows' example.

But what I'm saying is that his first picture didn't need to have the F. If the first Meadows example had no F, we'd interpret it the exact same way according to Y14.5. So is there some magic symbol to connote that a part is non-rigid? No.

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

 

[CheckerHater]

F combined with FCF overrides the rule that form tolerance must be refinement of size dimension. So different meaning indeed.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

F combined with FCF overrides the rule that form tolerance must be refinement of size dimension.

No it doesn't. That would be the I modifier.
F just means the FCF shall be checked in the free state. But this all illustrates an inconsistency in the standard. Yes, Fig. 5-13 uses the "F" but that's not needed if you really read para. 4.20.

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

 

[CheckerHater]

Just read the book:

From ASME Y14.5-2009:

Para. 5.4.3: “The circularity tolerance must be less than the size tolerance…”
Para. 5.5.3: “Note that the free-state circularity tolerance is greater than the size tolerance on the diameter” (Fig. 5-13)

Look at the accompanying illustrations: circularity tolerance without F are less than the size tolerance, circularity tolerance with F are greater than the size tolerance.



"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

I believe you are familiar with the "I" -- what does that mean in regards to the relationship between size and form?

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

 

[CheckerHater]

Sorry, I don't follow. Are you trying to steer the discussion in different direction?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[Belanger]

No, I was challenging your statement that F nullifies Rule #1. Agree that that's the job for I?

I guess I'll repeat my point: This all shows that there are paragraphs in the standard you can lay side by side, and there will be inconsistencies (or at least ambiguities).

A) Free state is the default.
B) Size tolerances control form (in ASME).
C) Free state modifier signifies a free-state check.

Clearly, statement C isn't necessary because of statement A. (The exception there is if a general restraint note.)
You're saying that statement C nullifies statement B. I guess I get that only because F seems to be otherwise useless in Fig. 5-13.

But can we agree that something is weird about all this? Maybe they need to re-write paragraph 4.20.



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