Bolt Hole with composite TP

Hi gang, long time no see

. It's been a while since I played around with CMM so please take it easy on me.

I have a typical cylindrical feature, a flange with OD and a bolt hole pattern. The callout to the 8 holes is TP.005AB and composite TP.001A.

Datum A is a face and Datum B is an OD.

How do I approach the first TP callout and second?

Do I have to use BF alignment with Rotate only for the first segment or not? And how to approach the second segment? If my memory serves me right, I would have to use BF alignments with Rotate only to get the first segment, but I am not sure about the second. HELP.

Neil Challinor over 2 years ago

What version of PC-DMIS are you using? If you are running a recent enough version (2020 R2 onward) I would strongly advise using the new geometric tolerance command.

This was a good discussion centred around trying to create a composite position of a bolt hole pattern using legacy dimensioning: https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/511591-composite-true-positions-in-legacy#post511591. However, you'll notice I joined the discussion towards the end (post #16, page 2) to point out a number of pitfalls in doing it that way.
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WolfMan over 2 years ago in reply to Neil Challinor

Thanks. Can you explain to me what exactly does second segment do? Does it eliminated the rotational deviation and only captures Hole to Hole deviation?
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Neil Challinor over 2 years ago in reply to Neil Challinor

The upper segment controls the pattern as a whole (PLTZF). You have a primary datum plane (A) and secondary datum cylinder (B) so your pattern of holes must maintain their relationship to each other along with their orientation to A whilst rotating around B until the pattern's position is optimized.

The lower segment controls the relationship of the features within the pattern (FRTZF). The holes must maintain their orientation to A but are free to translate within the smaller tolerance zones in order to optimize their position to each other but must not move outside the boundary of the upper segment tolerance zone.

See ASME Y14.5 - 2018 sections 10.5 to 10.5.1.1 and fig 10.39
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