Would this part be out of specs ? 1

[kakalee1]

This is a hypothetical example, but it is applicable to a lot of my company's parts. I would like to get a better clarification on this.

We use ASME Y14.9-2009. Attached is the drawing to give a better visual representation.

Basically, if I have a plate with a pocket that calls out .040 +/-.002, I would assume that the flatness on the bottom of the pocket to be less than or equal to .004. I know this isn't exactly the envelope rule (rule #1), but it is very similar.
However, the actual part is bent once it is un-clamped from the machine. The local depth of the pocket is still within tolerance .040 +/-.002, but the total height is .092 (just hypothetical) due to the deflection. Thus, this part is not within specs.

1. Is it correct to reject this part?
2. Is it correct to assume that the bottom of the pocket has to be within .004 flat based on the limit of size of the .040+/-.002 ?

All helps are appreciated.

Thanks.

 

[CheckerHater]

Your .040 dimension is NOT A SIZE. so Envelope rule or something "very similar" does not apply.

So far your specs are ambiguous, and their interpretation may vary.

To define your pocket better you have to apply controls like Parallelism, Flatness, etc. in accordance with ASME Y14.9-2009

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

 

[powerhound]

I agree with CH. Too much ambiguity.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[Belanger]

Agree. But another point to realize is that "free state" is the default condition for measuring the dimensions/tolerances. So unless there is a restraint note on the print, it should be checked without clamping forces anyhow.

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

 

[kakalee1]

@Belanger: I agree with you, and I also believe it stated in the book somewhere that unless otherwise stated, all dimensions are inspected at free state. That is actually why I thought the part should be rejected. Even though the "local" distance between the pocket and the top is within tolerance, the total distance would be out of out specs due to deflection.

@CH: I agree that the pocket needs to define better like you stated. However, if it is just defined as in drawing, can we come to a conclusion? Or like you said, the drawing is too ambiguous that no conclusion can be drawn.

For hypothetical purpose, can the pocket depth even be checked properly?

Thanks for all the helps.

 

[CheckerHater]

I already mentioned that your dimension is not a "size". Alternative to "size" is what is known as "point-to-point measurement".

As soon as you ask yourself "from which point to which point?" you'll realize that 2 people will have 3 opinions about possible conclusion.

So, I'm afraid not.

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