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tell me why this tolerance is wrong

Hi everyone

I have been having an animated discussion with the design engineers this morning as to why I think there drawings is wrong. The design engineer is sat there with the standard which is ISO 8888 and is adamant that he is correct and he can dimension the feature like this and use whatever tolerances he likes in whatever order.



That is the offending tolerance, A,B & C are the overall datums for the whole part and I have no problems with that segment. The lower segment however to me is wrong in so many ways, maybe I am wrong as I am someone who is actually trained in ASME and not ISO, maybe he is right and it can be done like this in ISO,

He claims the F in the circle means measure in free state however ive never seen it placed where it is now. I also believe from my ASME training that the bottom segment refines the top segment so cannot use different datums, and I think this is the same for ISO.

I would usually argue my case louder but this is the senior design engineer here and he is digging his heels in at the moment and not changing the drawing, plus I don't want to look like an idiot if he is right and can tolerance the feature like this.

Anyone have any thoughts?
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  • The FCF should be split to two callouts as they don't share the same datums (a must for composite). I believe this is the exact same for ASME and ISO. PC-DMIS will throw a tantrum if you try to build this composite FCF in XactMeasure (because they have different datums). The (F) means in free state, which logically should apply to the upper segment as well (if they were two separate FCF's, this wouldn't be a problem).

    Also, the tolerance zone seems to be one-axis (non-cylindrical)...

    Good luck?
Reply
  • The FCF should be split to two callouts as they don't share the same datums (a must for composite). I believe this is the exact same for ASME and ISO. PC-DMIS will throw a tantrum if you try to build this composite FCF in XactMeasure (because they have different datums). The (F) means in free state, which logically should apply to the upper segment as well (if they were two separate FCF's, this wouldn't be a problem).

    Also, the tolerance zone seems to be one-axis (non-cylindrical)...

    Good luck?
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