4 Replies Latest reply on Jul 5, 2015 11:17 PM by Peter Thannhauser

    ordinate dimension plus minus zero datum

    Peter Thannhauser

      Is there a way to force the ordinate dimension to show plus or minus deviation from the established zero datum? Attached pic shows example what I'd like (red values illustrated).

        • Re: ordinate dimension plus minus zero datum
          Peter Thannhauser

          Oops, I should have also mentioned, these circles are sketched on the drawings. They are not hole features in a part.

          • Re: ordinate dimension plus minus zero datum
            Kelvin Lamport

            Not by default. The usual manual workaround is to add the - sign to a dimension, then create and save a dimension Style and apply that to other dimensions.

            2014 SOLIDWORKS Help - Style

             

            Another way is to pre-select all the target dimensions and add the - sign en masse.

            • Re: ordinate dimension plus minus zero datum
              Kevin Chandler

              Hello,

               

              Until you specifically establish the X-Y axes on the drawing, I don't believe there are "positive" or "negative" dimension values because there is no establish reference to dictate plus or minus.

              Left reading/bottom reading drawings don't imply this.

              Without reference axes (a coordinate system reference), all dims are just values that are left/right or up/down of their dimension origins.

               

              Ordinate dim values, like all other dim types, are simply the distance from the chosen dimension origin (it's not a datum, at least not in the image--I know, splitting GD&T hairs) along the ordinate dim entity's alignment vector.

               

              Not that there can't be negative dimension values on drawings. I believe the Hole Table feature can have negative dims, but it establishes an X-Y reference.

              Ordinate dims don't have this coord system reference capability,

               

              I'm assuming your drawing doesn't indicate reference axes, but i'm not recommending adding the X-Y reference.

              By doing so, you're adding fabrication process instructions, which technically, aren't supposed to be on drawings.

              Even without the X-Y reference, specifying negative values adds fab instructions.

               

              Lastly, I try not to hard-code anything, if at all possible, because sooner or later, I'll get bitten.

               

              So, per the above blather, I'm recommending that you don't +/- ordinate dims (outboard of tolerances).

               

              Just my tuppence.

               

              Cheers,

               

              Kevin