7 Replies Latest reply on Jul 14, 2015 7:40 AM by Will Schmidt

    How to fit two swept cut threads together

    Will Schmidt

      I used swept cut with a triangle profile and a helix path to create custom threading on two separate parts.  Now the trouble is getting the threading on the two parts to match so that they can be screwed together.  I've tried a lot of different things and I'm not sure how to do this with certainty, and I can't get the screw mate to work.  Any help is appreciated!

        • Re: How to fit two swept cut threads together
          Jamil Snead

          Are you wondering how to calculate the correct clearance so that the parts will screw together in real life? Or are you just wondering how to align them in a SolidWorks assembly so that it looks like they are mated properly?

            • Re: How to fit two swept cut threads together
              Will Schmidt

              I want to design it so that they will screw together in real life, and I assume that them mating properly in Solidworks will follow from that.  I'm very fundamentally confused on how the two threads need to be geometrically aligned in order to screw together, and even if it works hypothetically perhaps this doesn't take into account an allowance between the two metal surfaces.  I've been looking at a lot of tutorials, but I can never seem to get it to work the same way.  But the main point remains: those two parts need to screw together in real life with a very good seal, and I even need to take into account that a gasket (probably 1/16") will need to fit underneath the top screwing part.

                • Re: How to fit two swept cut threads together
                  John Stoltzfus

                  With out looking at what you're doing - here is what I would do;

                   

                  Both the bolt and nut helix geometry has a starting point and a starting angle and if you match those two they will align perfectly, if you center the cut sketch to the helix.

                   

                  So let's say you use the top plane as a base, wherever you want the nut positioned in relationship to the bolt, the difference between the end of the bolt and the "top" of the nut, that is where you start your thread, say the bolt protrudes .25" pass the nut, that is where you start the helix on the nut. 

                   

                  Make sure you have the same starting angle on both parts, then your mates would be concentric and the distance of offset and a coincident or parallel to the front of right plane.

              • Re: How to fit two swept cut threads together
                Jan Forkovic

                Hi,

                setup assembly unit system to the same as part unit system (metric vs inch). In second correct thread diameter

                • Re: How to fit two swept cut threads together
                  Will Schmidt

                  Thank you both!  Screw mate is now working and the threads seem aligned.  I'm still slightly confused about matching the thread depth and the diameters of the parts/helix's so that I'm completely sure they will thread in real life.  My threads go in 1.5 mm, so I figure the extrude diameters and thread diameters for the "bolt" and "nut" need to match up (88.5 mm and 90 mm).  Jan's file shows a slight gap between the threads in cross-section view on the assembly, and I thought adjusting the dimensions would close this gap, but it didn't.  My final questions is, will the assembly that I'm attaching now actually thread together tightly in real life (just a few changes from Jan's)?  Should any dimensions be adjusted for a tight thread, or for an allowance between the surfaces, or any other reason?  Your help is invaluable, once I get this down I can do it for other projects easily!

                    • Re: How to fit two swept cut threads together
                      John Stoltzfus

                      I have a couple of suggestions, however it's your part

                       

                      Bottom Pc  - You have the thread start at the top and you work your way to the bottom, where you start your thread there is a little triangle remaining, you can clean that up by clicking on the triangle and then adding a cut extrude through all, this would make the cut on a tangent.  Or you can do a reverse helix and run the cut up, that would be a true representation, However I would have started my thread off of the surface you picked, if you start your cut 20mm off of the top surface, you would have a clean start.

                       

                      I'd do the same with the top part...

                       

                      I would also add a thread relief on both pcs.  A machine shop wouldn't be able to make them as shown, all you need to do is add a rectangular sketch and do a cut extrude revolve...