3 Replies Latest reply on Jun 16, 2017 12:57 PM by Dan Pihlaja

    GTOL interpretation

    Mike Agan

      Discuss: Should datum C have no profile tolerance? (Sample drawing-ignore other errors)

        • Re: GTOL interpretation
          Dan Pihlaja

          Datum C doesn't have a profile tolerance applied to it in that drawing.

           

          Are you asking SHOULD it?

           

          If you are assuming that the profile tolerance that is there is also applied to the surface that datum C resides on, then it doesn't.  At least it isn't in this print.

           

          Right now, the profile tolerance ONLY applies to R.3750 feature.   If you wanted it to apply it to the tangent features, the proper way is this:

           

          But in general, it is not good practice to include the datum in the thing that is being tolerance.

            • Re: GTOL interpretation
              Mike Agan

              Thanks. So now I've excluded Datum C, what of the .170 dim?

                • Re: GTOL interpretation
                  Dan Pihlaja

                  Well, that starts to get a little complicated:

                   

                  If you are putting a GTOL on the .25 hole (like a position tolerance), then leave it basic.

                   

                  If you are NOT putting a GTOL on the .25 hole, then you need to make the .17 and 1.25 dimensions NON basic and give them tolerances.

                   

                  Personally, I would put a Perpendicular (or position, but a position tolerance to a single planar datum is the same thing as a perpendicular callout) callout on the .25 hole Datum B.  Then you can leave it basic and all is good.

                   

                  Edit: Scratch that......After thinking about it, the 1.25 dim needs to stay basic and the .17 dim needs a tolerance.

                   

                  Although I would also re-order your datums in your Profile GTOL.   I would make them B, then A @max, then C.  Using the flat surface of A to check that feature would be easier.  Unless there is a reason you want the hole as your primary datum.  Then leave it.