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Bad GD&T prints

Calvin.Korver
Link to print https://drive.google.com/file/d/1PPWkIpGwM39PPnNyxP7Zwe0Rr7QkaRxh/view?usp=sharing

Only sharing part of the print for nondisclosure purposes, but there was a lot wrong with it. Thought I would share this since it has been so annoying for me.

They put a position dimention on many of the faces when they clearly needed/wanted a surface profile.
They also had an M modifier on almost everything including: datums that are planes, flatness, and one distance dimension

Currently talking with my contact to see if we can get this straightened out.

Anyone else deal with some bad GD&T?
  • in reply to dwade
    I would agree.

    I worked in medical for about a year and I once had a print with 9 datums defined on it, ABC were all parallel, and of the 9 datums only one of them actually was applied to control a feature.
  • in reply to Wes Cisco
    Thanks, I will have to check that out. I don't have a hard copy reference book with me in the shop it would be nice to pick up. I knew it was possible to get a position of a surface, but with the other fishy stuff going on I sent them an email, and got the ok to change some things.
  • Follow-up Post: I talked with the engineer and he thinks they do actually want the position dimension of the plain, even though I'm not convinced. I double-checked the print and it is to the ASME Y14.5-2009 standard. I don't think it gets any good data and I have been running the part and it says the planes are in the wrong spot along the plain getting numbers all over the place. Can someone give me a good resource as to what the true position of a plain is really measuring? Or what do tell the engineer bc I think you can only have this type of callout in some ISO standard.
    These parts are also getting a coating so I have added that to the tolerance already. I know that could be affecting the results, but the results still say its WAY out.


  • in reply to Calvin.Korver
    FYI.......its plane....Engineer might be more responsive to your suggestions this way.....
  • in reply to Calvin.Korver
    What? Engineers can't spell. Many don't even communicate in complete sentences.
  • in reply to Calvin.Korver
    stop PLAY-IN around guys calvin needs your help
  • in reply to Calvin.Korver
    Whoopsies, thankfully I have mostly been talking with a middle man over the phone so they have only seen some of my abhorrent spelling haha.
  • Follow-up Post: I talked with the engineer and he thinks they do actually want the position dimension of the plain, even though I'm not convinced. I double-checked the print and it is to the ASME Y14.5-2009 standard. I don't think it gets any good data and I have been running the part and it says the planes are in the wrong spot along the plain getting numbers all over the place. Can someone give me a good resource as to what the true position of a plain is really measuring? Or what do tell the engineer bc I think you can only have this type of callout in some ISO standard.
    These parts are also getting a coating so I have added that to the tolerance already. I know that could be affecting the results, but the results still say its WAY out.




    Howdy Calvin,

    Start with 7.2 POSITIONAL TOLERANCING on page 120 of ASME Y14.5-2009.
    The first sentence is
    Position is the location of one or more features of size relative to one another or to one or more datums.

    Planes are not features of size.
    This should be a profile control.

    If you can't easily communicate with the engineer or if they still insist this ought to be position after you refer them section 7.2, then I would suggest double dimensioning the plane. Once as position and once as profile. If it were me I would include a comment in the report stating that position is not an allowed callout per ASME Y14.5-2009 because position can only be used for features of size and planes are not features of size, therefore the double dimension on the report.

    Sometimes you can't save stoopid from itself, but you can protect yourself with transparency and clear specific citation of the standard.

    HTH & ymmv
  • in reply to DAN_M
    Bachelor's degrees in industrial engineering still get just get ONE week of curriculum related to GD&T at ASU.
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