concentricity

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  • concentricity

    I have a cylinder with 3 bores all in line. the first diameter is dat. k the next diameter is not a datum, and the third is dat.f........The print calls for the concentricity of the second diameter to k-f. Do I create an alignment to k-f then dimension the conc. to either of the diameters?

  • #2
    could you post a pic of the drawing please (or a portion thereof)?
    Thanks,
    Kevin
    RFS Means Really Fussy Stuff

    When all you have is a hammer - everything looks like a nail....
    sigpic

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    • #3
      How I would do it

      I see this kind of call out a lot. If possible measure one autocylinder that takes hits on both datums. If this is not possbile to due to different diameters or location on part, then measure a circle on each datum with at least 7 hits for each circle. (Use an odd number of hits.) If the gods are on your side you will be able to create a cylinder from the two circles. Be careful, pc-dmis may use you data to create somekind of monster cylinder with wrong diameter and vectors. If it does make a good cylinder, then treat it as one datum and make an alignment that levels to it. If it does not make a good cylinder you will have to use the two circles to create a 3D line. Create an alignment by leveling to the line, then use one of the datum circles for origin. ( Use your best judgement as to which one.) Make sure you check the location of both datum circles after the alignment to make sure it is correct. HTH
      sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

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      • #4
        Quick drawing

        See if this helps
        Attached Files

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        • #5
          I kinda thought that I needed to create a 3d line, level, and origin to one of the cylinders...wanted a little input

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          • #6
            yes 3D line

            3d line is best way I know of .

            sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

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            • #7
              I hate that datum deal with the hyphen (A-B). I'm not sure it is even legal. One of our suppliers asked us to add it to one of our drawings for a part they supply during a design review and against my protests our engineers added it anyway. Not only did they add it but they picked it up as a convention and use it on other drawings. Best part is I can't get them to interpret it. The best answer I get it "It means it has to run true to both datums". I say to them "why don't you control the two features back to one datum instead of controlling one to some made up datum structure like this A-B crap?"

              Funny how it works, if one of our suppliers wants a drawing change they get what ever they ask for because it might effect delivery. If one of us manufacturing guys asks for a change engineering acts like we are telling them how to do their jobs and doesn't give us squat. They know good and [email protected] well we aren't going to hold up delivery even if the drawing can not be interpereted. If we do it is our a$$ and that is not engineerings problem.

              Ayway I am done ranting, I hate that callout.
              <internet bumper sticker goes here>

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              • #8
                I think Wes gave some good advice.
                I was hoping to see the FCF in question. This looks like more of a total run out application...
                Kev
                RFS Means Really Fussy Stuff

                When all you have is a hammer - everything looks like a nail....
                sigpic

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                • #9
                  I'd go with the 2 circles
                  sigpicSummer Time. Gotta Love it!

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                  • #10
                    You don't have to set origins to either circle. It would be easier to analyze because you zero out the X/Y of the datum circles.

                    You can set datum to k then take middle diameter then insert concentricity. Set the datum to f then do the same. It really doesn't matter, PCDMIS just calculates the difference between the two anyway.

                    Align the Plane and use circles.
                    I used to be high on life but I built up a tolerance.

                    Brown & Sharpe Global Advantage
                    PCDMIS CAD++ v2011mr2
                    PH10MQ/SP600M


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                    • #11
                      Originally posted by kbotta
                      I think Wes gave some good advice.
                      I was hoping to see the FCF in question. This looks like more of a total run out application...
                      Kev
                      Here is the thing I was ranting about. It can't be legal, our engineers can't tell me what it means yet they are putting it on other drawings as well. Stupid, just plain stupid. I circled in red the lunacy.
                      Last edited by craiger_ny; 06-09-2006, 08:07 AM.
                      <internet bumper sticker goes here>

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                      • #12
                        One diameter is the C datum, one is the D datum, then each one has to be within runout 0.002" to the line from C to D. What it boils down to is they want a 0.002" roundness held on each diameter, that is all that can be 'pulled out' from those callouts.
                        sigpic
                        Originally posted by AndersI
                        I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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                        • #13
                          i would measure the two dias k&f and create a 3d line between the two. then level & origin to the line. then measure the middle dia and dimension the concentricity. this will be evaluated as concentricity between the axis which i believe the print implies.
                          Last edited by george frick; 05-12-2006, 08:38 AM.
                          sigpic
                          Southern Man don't need him around anyhow!

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                          • #14
                            Yes it is 'leagal'. The 14.5 standard even gives a sample of this.
                            There is Figs on
                            pg 173 FIG 6-21
                            pg 68 FIG 4-21

                            And an explanation on pg 67 4.5.7.2

                            This shows it 'legal', and what it means. Absolutly correct.
                            Kevin
                            RFS Means Really Fussy Stuff

                            When all you have is a hammer - everything looks like a nail....
                            sigpic

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                            • #15
                              Although, nose pickers application seems a little funny...
                              RFS Means Really Fussy Stuff

                              When all you have is a hammer - everything looks like a nail....
                              sigpic

                              Comment

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