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Thread: Number of decimal points for a spec?

  1. #1
    Associate Engineer
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    Apr 2012
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    Number of decimal points for a spec?

    Ran into a situation at work that is raising some questions.
    The spec on the print is listed as .25" -.03".
    Unfortunately there was a mess up on the machine and many of the overall heights were measured by a digital indicator around .2504".
    Is it implied that the .25" max listed on the print means .250000000000000..." max or is does the measurement device only need to read to two decimal places? Not that its only accurate to 2 decimal places but the it is only being read to 2 decimal places.

  2. #2
    Administrator Kelly Bramble's Avatar
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    Most correctly, all limits are absolute, regardless of the number of decimal places. The limits are interpreted as if they where continued with zeros - forever.

    But I'm sure common sense is allowed and often parts with miniscule out of limits are pushed through with the proper review and documentation.

    As far as measurements the gauges or your CMM are typically required to be 10x more accurate than the total allowed variation given by the tolerances.
    Last edited by Kelly Bramble; 04-17-2012 at 08:12 PM. Reason: Spelling

  3. #3
    Technical Fellow
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    Welcome to the forum. Dimension tolerances are a real hornet's nest of confusion. Some might say that two decimal places means two decimal places and who cares what is in the third spot.

    Others might say since no upper tolerance was given only an undersize allowance the 0.25" is absolute.

    Regardless of outcomes and opinions here, learned or otherwise, your ONLY avenue with this is to ask the client as to what is acceptable. Any other course of action is likely to cause great heartburn within your organization if they ship the 0.2504 and the client's incoming-QC rejects them. The bigger risk there is never getting more work from that client because you didn't get it right and then didn't ask and tried to slide something past.

  4. #4
    Associate Engineer
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    Thank you very much guys.

  5. #5
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by sspbass View Post
    Thank you very much guys.
    You're very welcome!

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