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The quick:

I've come up with a handful of possible options for how to structure the Datum Reference Frames (DRFs) and Feature Control Frames (FCFs) for this part. I've narrowed it down to the two shown below, but I don't know which is better, or if there is maybe another way of doing this I'm overlooking. I believe both are compliant to ASME Y14.5-2009, and I'm leaning towards option 1, but I wanted to get another set of eyes here to make sure the intent is understandable and clearly communicated. ASME Y14.5-2009 is a drafting standard, used in the U.S. and other countries to ensure prints are created and interpreted the same way across geographic and cultural divides.

DRF construction options

The dirty:

This is a cast part. It is cast to near net shape and then machined to final specifications. I need to check both the relationship of the machined features to each other and some of the machined features to the casting.

In checking the machined features to each other, I want to check the position of one group of features (hole pattern) to another group of features (different hole pattern). For this, I've simply declared the first set as a datum feature, and created a compound true position FCF for the other set using the first set as the secondary datum.

Now, for checking the first set to the casting, I need to check each machined feature individually to it's cast member. I'm struggling with how to apply a datum using the "INDIVIDUALLY" requirement (as defined in section 7.4.8, and figures 7-26 and 7-37 of ASME Y14.5-2009) to these holes for this FCF, while also maintaining the group datum for the other FCF.

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    $\begingroup$ This question might benefit from explaining the different acronyms you've used, and maybe give a little relevant background for why you're asking the question (ex. what is ASME Y14.5-2009, and why are you required to meet it). $\endgroup$
    – grfrazee
    Aug 11, 2015 at 19:38
  • $\begingroup$ The acronyms are defined in ASME y14.5-2009 ;) FCF = feature control frame. DRF = Datum reference frame. ASME Y14.5-2009 is a drafting standard, used in the U.S. and other countries to ensure prints are created and interpreted the same way across geographic and cultural divides. $\endgroup$
    – CBRF23
    Aug 11, 2015 at 20:11
  • $\begingroup$ It would be more beneficial for you to explain these in the body of your Question. Comments have a tendency to disappear or be deleted at a whim, so having this information in a more indelible location is a good thing. $\endgroup$
    – grfrazee
    Aug 11, 2015 at 20:34
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    $\begingroup$ For the record, I think it's reasonable to assume that someone with expertise to answer this question would know how to recognize a code name. $\endgroup$
    – Ethan48
    Aug 11, 2015 at 20:47
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    $\begingroup$ @Ethan48 - agreed. I also think even if someone didn't immediately recognize the acronyms, if they were at all familiar with the concepts seeing the image with two options provided, where I circled the items in question, is pretty self-explanatory. At least I hope so ;) $\endgroup$
    – CBRF23
    Aug 11, 2015 at 20:50

1 Answer 1

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I realize this is a bit late, but in option one you reference Datum G 4X individually. This is not allowed per Y14.5, you either recognize Datum G as the full pattern or you need 4 separate datums. In the second option you've just referenced a pattern of 4 diameters as two Datums at the same time. This also is not allowed per Y14.5

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