Hi all,

In reading Jeffs I have concluded I know nothing of GD&T. I must brush up! However, as a production board manufacture I dont see a lot of "testing" going on from my customers by slipping in a global positioning requirements. Shoot, some of us have enought trouble still understanding true position ( haha ). I would suspect that when a customer puts +/- .001 on a print for a finished hole size tolerance that is EXACTLY what that customer is expecting to get. Expecially since I have found most designers ready and willing to keep it as simple as possible. Not to mention what the receiving inspection effort would have to say about complicating the requirements.   Just my two cents...


Ed Cosper

----------
From:   Jeff Seeger
Sent:   Friday, December 04, 1998 2:13 AM
To:     [log in to unmask]
Subject:        Re: [TN] Hole Tolerance of +/- .001"

Hugh Scott Miller wrote:
>
> Happy Holidays Technetters,
>
> A recent project has entered our shop from a customer that is demanding
> that all finished hole tolerances be held to +/- .001".  I pose the
> following questions to the esteemed Technet panel:
>
> a.  Are hole tolerances of +/- .001" realistic?

        My suggestion - question the drawing or at least
        be certain you are reading it correctly.

        Long ago, a company was (unbeknownst to me) testing
        us with a tricky mechanical print.  If one didn't
        understand GD&T (I didn't), one would think that a
        particular slot had a +/-.001" positional tolerance
        (I did).

        In a GD&T dimensioning scheme, you could be looking
        at a note that is telling you the tolerance for the
        holes relative to the global tolerance, but it looks
        absolute.

        Many thanks to John Sabo's presentation on Geometric
        Dimensioning and Tolerancing for opening my eyes on
        the topic, and giving me a belly laugh when I real-
        ized what had been happening 7 years earlier.

        Regards to all,
--

      Jeff Seeger                         Applied CAD Knowledge Inc
      Chief Dimensionally-Challenged Electronics Guy  Tyngsboro, MA
      jseeger "at" appliedcad "dot" com                978 649 9800

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