Reporting Position (GD&T)

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oldpunkrocker
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Reporting Position (GD&T)

Post by oldpunkrocker » Wed Jul 11, 2018 2:18 pm

Hello. I am looking for some input on how to correctly report position.

Normally, when I have a multiple single segment feature control frame (two or more separate position symbols) I just select the report position command two times and change the datums to those specified. I noticed the reported deviation is the same no matter which datums are used. Is this correct?

Second, on the attachment there are five M6 helicoils in the bottom part of the main view. For the first one from the left, no issue, just select report position command because there is only one feature control frame (FCF) and the basic dimensions are off the datums. For the second, also because basic dimensions are from datums, I would report as described above, by selecting the report position command two separate times with specified datums from each FCF.

The third fourth and fifth helicoils is where I am having the most confusion because the basic dimensions are from hole to hole in one direction, not from datum C. I think that maybe the FCF for the three holes is intended to be composite even though the FCF has two position symbols instead of one (or if not shouldn't the basic dimensions (375,750,1071) be locating from datums?). Is the composite command what you would use to report these helicoils? I know that there is a box that can be checked for whether or not there are one or two position symbols in the report composite command. From my understanding if a FCF has the two symbols it is considered a multiple single segment FCF and is calculated differently than a composite position so I am no sure why this box is there?

Anyway, any input on how anyone would report these features is appreciated. It is also possible that my drawing does not have GD&T correctly applied for the reasons above. To me my drawing seems conflicting.
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Ryan Christopher
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Re: Reporting Position (GD&T)

Post by Ryan Christopher » Thu Jul 12, 2018 12:19 pm

What standard is this drawing to? If the title block says ASME Y14.5 then the feature control frames are not written correctly. I'm not sure what the European standard requires.

In 14.5 the datums in the lower portions of the feature control frame need to be in the same order as in the ones above them.
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oldpunkrocker
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Re: Reporting Position (GD&T)

Post by oldpunkrocker » Thu Jul 12, 2018 12:58 pm

I believe we would be attempting to be compliant with ASME 14.5 but our drawings don't even list what standard we are going by.

On the highlighted FCF for example, are you saying that if you are using C, B and A in the top portion that A cannot even be used in the lower part unless C and B are used first? So the only way you could use A is if the order in the upper section is A, B, C? What if datums C and B are not desired in lower FCF? Is that an impossibility the way it is written?

Any input on the other parts of my post?

ccarne248
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Re: Reporting Position (GD&T)

Post by ccarne248 » Mon Jun 15, 2020 2:05 pm

Basically it is saying holes must be good to CBA w/in 10 and good to themselves w/4 when leveled on A

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