Odd Flatness Callout Please Explain
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  1. #1
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    Default Odd Flatness Callout Please Explain

    I have a customer that has to meet military contracts and tolerances. There is a OLD print we are going through that has an odd flatness callout. I have read thousands of prints and never seen it given this way. It makes sense to me that it is .005" per every .5" inches. In other words it would have to be flat within .01" and it cannot vary more than .005" per every .5"...

    The other question with this is if we have a flat surface and can fit a .005" feeler cage under the part for a 2" distance the part would be good still right? The .01" feeler gage does not go under the part so it is within .01" flatness. I know the best way to check is with an indicator (and part sitting flat) or CMM but I do not have a way to make either of these happen and the customer wants to use this flat plate and a feeler gage.

    flat.jpg

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    We work with very old drawings and this has been my understanding of that tolerance. .005 flatness for any .5x.5 area. maximum of .010 for the full surface.

  3. #3
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    Feeler gage isn't a really good way to check this, IMO.

    What's happening to the surface in the center, where you can't reach?

    If your .005 feeler gage goes under the part it may be good, it may not be.

    Correct way would be to set it on 3 equal stacks of gage blocks and sweep the surface with an indicator.
    It can neither rise nor fall more than .005 per 1/2 X 1/2 square.

    If your customer wants it inspected with a feeler gage on a surface plate, I would feel most comfortable with parts that would not accept a .005 feeler gage anywhere.

  4. Likes TeachMePlease, Pariel, Krutch liked this post
  5. #4
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    Thanks for the replies!


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