Inclusion of MIL-SPEC Rev. Letter in a Callout

[supercub]

A drawing for a part that is to be anodized calls out a MIL-SPEC for the anodizing. The note that calls out the MIL-SPEC included the rev letter after the spec, MIL-A-8625E. Looking up the spec online, I see that the rev had changed to F. Is it common practice to include the current rev letter after the MIL-SPEC callout as the specs do themselves, or leave out the rev letter?

 

[MintJulep]

Yes.

Regardless, you need to make a decision. Fortunately it is the same decision in any case.

Situation 1:

Revision not identified. --> You can assume that the revision that was current when the drawing was made was intended.

Has the standard been revised in the time since the drawing was made?
Do the revisions change the characteristics of the process in a way that alters the performance of the part?
Decision required: Make new part according to "obsolete" revision or current revision?

Situation 2:
Revision identified, AND the identified revision was the current revision at the time the drawing was made.

Has the standard been revised in the time since the drawing was made?
Do the revisions change the characteristics of the process in a way that alters the performance of the part?
Decision required: Make new part according to "obsolete" revision or current revision?

Situation 3:
Revision identified, AND the identified revision was NOT the current revision at the time the drawing was made.

Maybe the drawing creator just didn't know what was current.

Maybe the drawing creator had a specific reason to invoke an "obsolete" standard.

Decision required: Make new part according to "obsolete" revision or current revision?

 

[drawoh]

MintJulep,

I would exclude the rev letter and assume that the current specification would be used. Would the specifying committee change the specification such that the new finish was functionally different from the old one?

--
JHG

 

[3DDave]

drawoh - yes, there have been changes that make it different. The changes are usually stupid, such as changing class designations from "II" to "2." Sometimes the testing criteria changes. Sometimes methods are dropped, such as those which involve cadmium or chromium. Similar to the reason Y14.5 requires listing the year. I've gotten to spend too much time figuring out the significance of changes in MIL spec revisions. The 'good' news is that the DoD had its budgets for such things slashed and the COTS people ride in, which means - people just have to pinky swear their process meets the performance requirements rather than having to follow a defined process with known-good results.

<lengthy angry rant about selling off public specifications to private interests for private profit>

 

[MintJulep]

Yes, sometimes standards change in ways that actually affect things.

Sometimes things become more strict.

Sometimes things become more lenient.

Sometimes things become more expensive for the same performance.

Etc.

 

[drawoh]

3DDave,

Drafting standards are not the same thing as material finishing standards. ANSI/ASME Y14.5 tells us how to interpret codes on drawings. If a drawing is prepared to ANSI Y14.5M-1982, it must be interpreted by that standard.

If fabrication drawing calls anodizing to MIL-A-8625, does revision[&nbsp;]G provide a functionally different finish that revision[&nbsp;]F? On engineering drawings, keep thinking functionality.

--
JHG

 

[CWB1]

You should always callout the specific revision, otherwise you are letting a third party who does not know, understand, or care about your specific part's form, fit, and function affect your part. In your given example, E might allow for a functional design whereas F may allow the part to fail in an unacceptable manner. A very common misconception among junior engineers is that the latest rev must always be used whereas quite often older revs are perfectly acceptable.

 

[WKTaylor]

At my company, the standard is as follows...

[Spec][with revision letter/code/date] = use that specific spec revision ONLY [may request engineering waiver to later/latest* spec Rev]
[Spec][with revision letter/code/date]['..., or later rev'] = May use that specific spec Rev or any subsequent spec Rev
[Spec][with revision letter/code/date]['..., or latest rev'] = May use that specific spec Rev or may use latest* spec Rev [only]
[Spec][no revision letter/code/date] = Must use LATEST* spec revision.

[use = comply with]

*NOTE.
Latest* Revision in effect at time parts fab was contractually committed shall be used. This 'freezes' the configuration and allows uniform processing start-to-finish.
Exception: contract may specifically allow or mandate that subsequent 'Manufacturing Lots' meet latest ['most up-to-date'] spec revision at a specified point in multi-Lot fab process [TBD by the contract]. Caution... this can create part dissimilarities and/or fab confusion.



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[pylfrm]

At my company, the standard is as follows...

Does this standard define interpretation of you company's drawings, or is it used to standardize your company's interpretation of drawings from other companies?

[Spec][no revision letter/code/date] = Must use LATEST* spec revision.

While I can see some potential benefit to this choice, it seems a bit odd to disallow use of the revision that was current at the time of drawing creation.


pylfrm