4 Replies Latest reply on Jun 16, 2008 4:07 PM by Eddie Cyganik

    Correct Dimensioning

      Hi all,

      I just want to find out which way of dimensiong is correct on the 2 attached pictures or are both styles fine. I find the ordinate dimensioning tool very convenient to use as it's so much quicker.

      God bless,

      Phil.
        • Correct Dimensioning
          Dan Riffell
          Both styles are fine, depending on your company specifications, as long as you pay attention to the way you tolerance your drawings. That is, if tolerances matter for your parts. I find the scheme on the bottom a little more clear, though, but that is personal preference.
          • Correct Dimensioning
            Nigel Bennett
            "Correct" ? - in my experience, no drawing is ever 100% correct!

            Both ways of dimensioning the part are acceptable.

            There is implied symmetry in the bottom view, but how accurate does the symmetry need to be? What I'm driving at is that there are no tolerances shown that I can see, so the machine shop interpretation of what they make you may not be exactly what you want!

            The way in whiich you dimension a part will affect the way in which the tolerances add up. If you do ordinate dimensions from the one datum, then a pair of holes can theoretically vary in their centre distances by more (twice!) than if you dimensioned them with a centre distance between them, assuming the same general tolerance on dimensions.

            Hence the Geometric Tolerancing system(s) in use, which should fully determine what is and what is not acceptable. This is not the place to begin a discussion on the whys and wherefores of Geom. Tols, though!

            It's probably best to talk it over with who is making the part - they are your personal customer, and you've got to sell it to them. Bear in mind that the final product must go together, though!
              • Correct Dimensioning
                Eddie Cyganik

                Nigel,

                Based on your comment:

                Do you create drawings, check & approve them and only release them to a shop if they are 95% correct? or 90% Correct? or maybe, depending and the quality, 87% Correct?

                I for one, check drawings, mark them up and return them to drafters to incorporate the necessary changes. Once a drawing is drawn, checked & approved, it is 100% correct for the accuracy, quality and function required for the part and/or assembly.

              • Correct Dimensioning
                Eddie Cyganik

                Philip,

                I agree with Dan & Nigel, in that you can dimension your part using several dimensioning schemes, although, design intent (tolerancing) must always be considered.