3 Replies Latest reply on Jul 23, 2010 12:43 PM by Paul Marsman

    Tricky dims to datum? HELP!!

    Ryan Hudson

      I am going to attempt to explain this in the best way I can - with the minimal knowledge of GD&T that I posses.

       

      I need some input on the best way to dimension some surfaces/holes that get machined after a welding process. I just got a drawing from mfg asking how they make the part....and I don't normally handle this part type here, that guy is on vacation.

       

      Attached is a quick drawing of the dilemma. The part has a pattern of hooks and pads that are made around an axis that isn't currently called out on the latest revision of the drawing (attached as well). The current datum that is used is off a hole that is not common to the pattern.

      The first question I have is how would you accurately express that the cuts on the hooks and pads are centered along a revolving axis? I'm probably totally off on the explanation and I apologize, but I know very little about GD&T but I do know that it is very important that the hook slots and pad surfaces are consistent in each instance of the pattern. The bent part isn't controlled very well, so the machine step would ensure that the next assembly would prove out well....as long as we can convey that to the floor.

       

      Any and all help would be greatly appreciated. I'm sure I left something out so please ask me to clarify if you have specific questions.

       

      Thanks,

      Ryan

        • Re: Tricky dims to datum? HELP!!
          Paul Marsman

          are you able to attach the drawing and referenced parts/assemblies so I can get a better idea of what I'm looking at and just detail your drawing directly?

            • Re: Tricky dims to datum? HELP!!
              Ryan Hudson

              Paul,

               

              Unfortunately no, our company has an ultra restrictive IT policy, I may not have even been able to post what I did. Can you mark up the drawing easily?

               

              Thanks for looking into it!
              Ryan

                • Re: Tricky dims to datum? HELP!!
                  Paul Marsman

                  Ryan,

                    Fully understand, just trying to make it a bit easier to move info back and forth and I'm still trying to wrap my head around it a little.  Do you have access to a ASME Y14.5M book?  If not, GET ONE.

                   

                    I'm going to try and print this out and play around with what would be the best way to dimension and control what you are looking for.  To clarify also, you are looking to control the angle from the midplane of the slots on the hooks to the midplane of the slot to the middle hook?  Also, you are looking to contol the flats that get machined to be a certian distance from the center of the rotation axis (the item you identified as "DATUM?"  ?