29 Replies Latest reply on Jun 12, 2018 4:22 PM by Dan Pihlaja

    Drawing and Dimension

    Maha Nadarasa

      What is 2x2.75 dimension indicating? Adjacent two structure dimension?

       

      2018-06-12_10-13-25.png

        • Re: Drawing and Dimension
          Jeremy Feist

          it is the length of the 2 identically shaped bosses

          Capture.PNG

            • Re: Drawing and Dimension
              Maha Nadarasa

              What is meant by this reference dimension?

               

              2018-06-12_10-39-33.png

                • Re: Drawing and Dimension
                  Dwight Livingston

                  That dimension is specified in section B-B. Here it is referenced to help you interpret the dimension and the view, but does not specify anything.

                  • Re: Drawing and Dimension
                    Jeremy Feist

                    reference dimensions are on a drawing for reference only. their value and tolerance are defined by other dimensions on the drawing.

                    • Re: Drawing and Dimension
                      Dan Pihlaja

                      I just want to point out that, if someone turned this print in to me and told me is was complete.....they would be told to redo it.   This print was drawn by an amateur and NOT by anyone knowledgeable in creating engineering drawings.

                      I can't believe that this was created as a training tool, as it sets a HORRIBLY bad example.  Now that I understand what this drawing is for (simply a modeling challenge), I guess I understand why someone might have hurried through creating this drawing......but still....

                       

                        • Re: Drawing and Dimension
                          Maha Nadarasa

                          Thanks for the explanation. I will make a complete drawing with your suggestion after finishing the model.

                          • Re: Drawing and Dimension
                            Maha Nadarasa

                            Is this what you mean?

                             

                            2018-06-12_10-13-25.png

                              • Re: Drawing and Dimension
                                Dan Pihlaja

                                No, Not really.

                                Basically, this drawing leaves a lot to implication.  The notes that are on this drawing allow for a massive amount of error.

                                 

                                Missing dimensions are typical?   Seriously?  This is ridiculous and lazy (maybe a little harsh....but I don't like it)  Sometimes the word Typical could and should be applied.  But ONLY if there is 1 feature of that type being dimensioned and it is obvious that this feature is common throughout a part.    In this case it is ridiculous.

                                 

                                As far as note # 3.....if they want symmetry to be applied....put it on section C-C, as that is the ONLY area of the print that might have symmetry.  General notes are for the general drawing....

                                 

                                As far as how this is dimensioned.....well, there are not tolerances on this print...Not even title block tolerances......what are they?

                                 

                                Assuming that the .75 hole is dead center between the two holes is an assumption at best.  In fact, the dimension that shows 2.23 shows me that there IS NOT symmetry, because the dimension should be 2.22 if it were symmetrical.   If the dimension should be 2.23, then to which side of the .75 hole (top or bottom with respect to section C-C) should the shorter side be?  Because the distances between the .38 hole and .75 cannot be the same.

                                 

                                There is simply too much being assumed on this print.

                                 

                                Maha, where did you get this drawing?

                                  • Re: Drawing and Dimension
                                    Maha Nadarasa

                                    I will make this mode and attach the part file. It is helpful if you can make and attach a correct drawing file.

                                     

                                    SOLIDWORKS World: Model Mania 2000 - YouTube

                                      • Re: Drawing and Dimension
                                        Dan Pihlaja

                                        So this was the drawing used in the model mania challenge of SW world 2000.

                                         

                                        The way this drawing is drawn would actually make it harder to model in my opinion than if it had been fully detailed.

                                         

                                        As it is, the reference dimension of 2.23 just confuses the issue even more.

                                        AND on top of that, one of three things is obvious:

                                        1) Either the original model that this was drawn from had numbers in the CAD model that were CLOSE to the numbers that show on the print, but not exact (like the .38 radius)

                                        OR
                                        2) The 2.23 dimension was overridden for some silly reason

                                        OR

                                        3) The drawing was not made in Solidworks.

                                         

                                        I am sorry to those who might have created this drawing.....but I don't like it.

                                        I found it here as well.

                                          • Re: Drawing and Dimension
                                            Jeremy Feist

                                            also, how deep are these holes?

                                            Capture.PNG

                                            as someone who has participated in the model mania contest since 2011, I can say the drawings have gotten better

                                            • Re: Drawing and Dimension
                                              Frederick Law

                                              2.23 REF is correct.

                                              Welcome to the world of round up Imperial dimension.

                                              If dimension are 3 decimals, 0.38 may become 0.375 and 2.23 become 2.225.

                                              • Re: Drawing and Dimension
                                                Maha Nadarasa

                                                Part file is attached.

                                                • Re: Drawing and Dimension
                                                  Timothy Taby

                                                  The 2.23 vs. 2.22 dimension is likely due to rounding issues where 2.225 rounds up to 2.23 when taken to only two decimal places.  The 0.38 radius is mostly likely 0.375, which would makes the 2.23 dimension actually 2.225.  I would show a third decimal on those valves to make sure they add up properly when combined with the overall height dimension.  Yea, the drawing is not very good at all.

                                                    • Re: Drawing and Dimension
                                                      Dan Pihlaja

                                                      Timothy Taby wrote:

                                                       

                                                      The 2.23 vs. 2.22 dimension is likely due to rounding issues where 2.225 rounds up to 2.23 when taken to only two decimal places. The 0.38 radius is mostly likely 0.375, which would makes the 2.23 dimension actually 2.225. I would show a third decimal on those valves to make sure they add up properly when combined with the overall height dimension. Yea, the drawing is not very good at all.

                                                      Agreed......but if they wanted it as a 0.38 radius....then they should have modeled as a 0.38 radius and not a 0.375 radius.

                                                        • Re: Drawing and Dimension
                                                          Matthew Lorono

                                                          This isn't always realistic.  There are many reasons for decimal places to be truncated rather than modelled to the dimension, especially if the dimension is a reference.  Either way, SW allows you to round down if you wish for situations like this.  You can also round to even by default too.

                                                            • Re: Drawing and Dimension
                                                              Dan Pihlaja

                                                              Fair enough.  I guess that I have done it in the past.  Especially with a part that I modeled in metric, but the drawing was in inches.   Almost all the dimensions need to be truncated then.

                                                               

                                                              However, the issue still stands that symmetry is implied, but is not really clear in that drawing view.....especially since, using the dimensions supplied, they don't add up to the correct number for the reference dimension (which is what a reference dimension is for...for checking your work).  Honestly, it would have been better if that reference dimension either had enough decimal places to be clear or were left out entirely.

                                                               

                                                              I can model that part, but if it were a real world part drawing, I would be asking a lot of questions.  And attempting to get, in writing from my customer, the answer to those questions.

                                                               

                                                              I realize now that I took that whole thing a little too seriously, and misunderstood what the drawing was for, and I apologize if I might have ruffled some feathers, but in my line of work....if a drawing is unclear, questions need to be asked....because a part made incorrectly could mean that a lot of people get hurt.  At my previous job as a designer for a DOD suppler, the mantra was, "If you get it wrong, a soldier will die."

                                                                • Re: Drawing and Dimension
                                                                  Jim Steinmeyer

                                                                  Dan,

                                                                  Given your experience in working with DOD and Aerospace (if I recall correctly) you can be expected to be much more of a stickler for exactness on prints. That is something that has been very important in your industries. Here we have welders and fabricators who count the "little tick marks" between the 1" and 1/2" measurements, sometimes. Last week I had to explain to the shop foreman how a section view works and how to read it. Not a new welder, the SHOP FOREMAN! And he has been here over 30 years.

                                                                    • Re: Drawing and Dimension
                                                                      Dan Pihlaja

                                                                      Jim Steinmeyer wrote:

                                                                       

                                                                      Dan,

                                                                      Given your experience in working with DOD and Aerospace (if I recall correctly) you can be expected to be much more of a stickler for exactness on prints. That is something that has been very important in your industries. Here we have welders and fabricators who count the "little tick marks" between the 1" and 1/2" measurements, sometimes. Last week I had to explain to the shop foreman how a section view works and how to read it. Not a new welder, the SHOP FOREMAN! And he has been here over 30 years.

                                                                       

                                                                      Yes, DOD and aerospace, and that is what happened here.  I was using the criteria that I use here at work on a print that was meant for nothing more than a modeling challenge.  Yeah....I am starting to like the taste of crow.  LOL 

                                                              • Re: Drawing and Dimension
                                                                Maha Nadarasa

                                                                Though small it is making big difference.

                                                                 

                                                                2018-06-12_14-29-35.png

                                                          • Re: Drawing and Dimension
                                                            Jim Steinmeyer

                                                            Dan Pihlaja wrote:

                                                             

                                                             

                                                            Assuming that the .75 hole is dead center between the two holes is an assumption at best. In fact, the dimension that shows 2.23 shows me that there IS NOT symmetry, because the dimension should be 2.22 if it were symmetrical. If the dimension should be 2.23, then to which side of the .75 hole (top or bottom with respect to section C-C) should the shorter side be? Because the distances between the .38 hole and .75 cannot be the same.

                                                             

                                                            There is simply too much being assumed on this print.

                                                             

                                                            Maha, where did you get this drawing?

                                                            Dan, is the apparent inaccuracy in the print dimension possibly due to rounding errors? I suspect that if they went to 3 or 4 decimals you would not be seeing an error, just a guess.

                                                              • Re: Drawing and Dimension
                                                                Dan Pihlaja

                                                                Jim Steinmeyer wrote:

                                                                 

                                                                Dan Pihlaja wrote:

                                                                 

                                                                 

                                                                Assuming that the .75 hole is dead center between the two holes is an assumption at best. In fact, the dimension that shows 2.23 shows me that there IS NOT symmetry, because the dimension should be 2.22 if it were symmetrical. If the dimension should be 2.23, then to which side of the .75 hole (top or bottom with respect to section C-C) should the shorter side be? Because the distances between the .38 hole and .75 cannot be the same.

                                                                 

                                                                There is simply too much being assumed on this print.

                                                                 

                                                                Maha, where did you get this drawing?

                                                                Dan, is the apparent inaccuracy in the print dimension possibly due to rounding errors? I suspect that if they went to 3 or 4 decimals you would not be seeing an error, just a guess.

                                                                 

                                                                Yes, I believe that this is exactly what it is. 

                                                    • Re: Drawing and Dimension
                                                      Chris Saller

                                                      I would assume the other part at 45 deg. But, because you question it, someone else will too. The other 45 deg is called out at section B-B.

                                                      • Re: Drawing and Dimension
                                                        Maha Nadarasa

                                                        Thanks for all of you.