[ge...] Posted January 18, 2020 Share Posted January 18, 2020 good morning I have a doubt with the true position as I have understood this is not possible but I would prefer other opinionsDuda.png Link to comment Share on other sites More sharing options...
[Ja...] Posted January 18, 2020 Share Posted January 18, 2020 What is datum A? Can you post something that is easier to see? Link to comment Share on other sites More sharing options...
[ge...] Posted January 19, 2020 Author Share Posted January 19, 2020 Datum B and C are part of the same drawing I think this is not possibleDatum A.jpgDatum C.jpgDatum B.png Link to comment Share on other sites More sharing options...
[Ja...] Posted January 20, 2020 Share Posted January 20, 2020 I can't understand what you are asking or showing. Try opening your print in MS Paint and erasing all of the non pertinent information if possible, only leaving the characteristics (&datums) that you have questions about. Link to comment Share on other sites More sharing options...
[Da...] Posted January 20, 2020 Share Posted January 20, 2020 Please sign in to view this quote. I think it bothers him, because the 2 true positions depend on each other (or each others datum, or whatever). The theory could be to do the symmetry of 2 cylinders and throw that in secondary datum. Could be, I'm unsure. Link to comment Share on other sites More sharing options...
[To...] Posted January 20, 2020 Share Posted January 20, 2020 open picture in Paint and crop the image. Link to comment Share on other sites More sharing options...
[ge...] Posted January 21, 2020 Author Share Posted January 21, 2020 Datum B and C could interact or it is not possible20200120_212418.jpg20200120_212445.jpg Link to comment Share on other sites More sharing options...
[To...] Posted January 21, 2020 Share Posted January 21, 2020 In my opinion, I would say "No". Or, I don't think it is necessary or common. Is it legal? I don't know. Link to comment Share on other sites More sharing options...
[De...] Posted January 21, 2020 Share Posted January 21, 2020 I don't see anything wrong with these call outs. They each have their own Datum Reference Frame and therefore are not required to meet any simultaneous requirement. Taken individually there is no issue with either one. They are inter-related to one another due to the fact they both use the other as their secondary datum reference, however that should not pose a problem so far as they fall within the specified tolerance zone. It appears that Datum C is essentially controlling the location of Datum B, so as Datum C moves within its 0.100 zone, the 0.015 tolerance zone for Datum B must 'follow' it around. This seems like it would make sense in order to create a pattern to mount something, and allow the entire pattern to shift around while maintaining positioning to one another. Usually this is handled using composite true position but this method seems to accomplish the same thing. Link to comment Share on other sites More sharing options...
[An...] Posted January 21, 2020 Share Posted January 21, 2020 Please sign in to view this quote. I agree. It's necessary to check the perpendicularity of datum B. This is done by the True Position callout related to datum C. Link to comment Share on other sites More sharing options...
[To...] Posted January 21, 2020 Share Posted January 21, 2020 Why would I need to check the position of B to C? There is a +/- dimension from one edge and a BASIC dim to another edge(?). A position of B to A controls the orientation. And, a position of C to A and B controls the orientation and location. I think a position of B to C is the tail wagging the dog.... The relationship between datum features to be considered are the: (a) form of the primary datum feature(s) and/or the location between features in a pattern to establish the primary datum. (b) secondary datum features' orientation and/or location as applicable, to higher precedence datums. (c) tertiary datum features' orientation and/or location to higher precedence datums. Link to comment Share on other sites More sharing options...
[An...] Posted January 22, 2020 Share Posted January 22, 2020 Please sign in to view this quote. Nut sure what the above means. See attached.Contribution_22_01_2020_a.pdf Link to comment Share on other sites More sharing options...
[To...] Posted January 22, 2020 Share Posted January 22, 2020 Please sign in to view this quote. I was pointing out that B has something to locate from other than C. Sorry, I wasn’t more clear. Link to comment Share on other sites More sharing options...
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