Quality Assurance Inspection-Octagon Symbol?

[EngineerErrant]

At my previous job, my employer utilized a particular symbol (an octagon with some three-letter acronym inside, I think) to indicate dimensions which were crucial for performance, and should be inspected both after manufacturing and before assembly. He assured me that it was a standard. (I believe he said it was for SAE, but I could be wrong.)

Google has netted me nothing - does anyone know what I'm talking about?

"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." -Scott Adams

 

[CheckerHater]

You are talking about “critical dimension” and “critical dimension symbol”; both already beaten to death on this forum.

No, there is no standard for it. Ask your boss to produce the book that says otherwise (do it on your own risk).

The “correct” way would be to pick symbol you like and EXPLAIN it on the face of the drawing, as in: “dimensions marked with this symbol to be checked according to quality procedure No. 12345”.

The reason for this is that identifying critical dimension is part of manufacturing/quality control process, rather than design process and your prints are to be as procedure-independent as possible, so your inspection plan belongs on the separate sheet of paper.

For more information you can search this forum for “critical dimension” and “critical dimension symbol” using search field above to the left (the one that says “Google(tm) custom search”).

 

[dgallup]

The obsolete QS-9000 goes into extensive detail about special characteristic symbols. Unfortunately, it does not go so far as to standardize them, instead it leaves them up to the OE automotive companies to define their own. It lists Chrysler, GM & Ford symbols and definitions, none of them are an octagon. It also lists 6 other automotive companies that have adopted QS-9000 and their respective publications with their requirements.

TS-16949 has replaced QS-9000, it does not give any special characteristic symbols, just says to use what your customer requires. That's great if you supply the same part to multiple customers.

We do what Checker-Hater said, made our own symbols and put a key on the drawing referencing our document that explains them except in the case of a customer specific document where we use the customer symbols.

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