11 Replies Latest reply on May 1, 2017 10:01 AM by Maha Nadarasa

    Thread Cutting

    Maha Nadarasa

      In this video a line in cutting profile and a line in part is selected to make both collinear then Helix/Spiral and cutting profile is selected to cut a thread.  

       

      My question is, what is reason for making collinear?

       

      SolidWorks tutorial | Design And Assembly of Pipe vise in SolidWorks - YouTube

      Time 55.03-55.12

       

      1.png

        • Re: Thread Cutting
          J. Mather

          Uhmmm, to make the lines colinear, to line up the cutting tool with the edge of the hole.

           

          But there were several mistakes made in my view.

          The angle of the Helix should be changed so that it matches the start of the Sweep profile sketch.

          The sketch should have also been constrained to the end of the Helix.

           

          (Note at the other end that the thread does not appear complete in the video - therefore the mechanism will not work.)

           

          Attach your *.sldprt file here for correction.

            • Re: Thread Cutting
              Maha Nadarasa

              Here is the file

                • Re: Thread Cutting
                  J. Mather

                  Cutting Tool Burried.png

                  Note that the Start of the Helix is not connected to the tool profile - poor practice.

                  Note that the tool is already buried into the part - poor practice and not possible in the real world cut.

                  The tool cutting action should start at the edge of the part.

                   

                  Start Angle.png

                  Note the change in Start angle (or you could change the sketch plane for the cutting tool profile).

                  Better.png

                  In the attached file I -

                  1. Increase lead-in chamfer size and added lead-out chamfer on other end.  This helps keep thread from getting "galled-up" in real world use.

                  2. Moved the start angle of the Helix and change location of the cutting tool profile outside of the part (just like the real world).

                  3. Got rid of the 1.11 dimension and replaced with 1.5 (equal constraint to pitch) at the pitch diameter.

                    • Re: Thread Cutting
                      Maha Nadarasa

                      I couldn't understand what you mean by "galled-up" and equal constraint to pitch.

                      1.png

                        • Re: Thread Cutting
                          J. Mather

                          After repeated use the threads do not move smoothly.

                           

                          galled.png

                           

                          I should have written Pitch/2 as the Pitch = 3.

                          Some of this is so obvious that you should be able to figure out by careful observation.

                           

                          Pitch.png

                            • Re: Thread Cutting
                              Maha Nadarasa

                              After repeated use only parts wearing can take place accordingly on each other and smooth movement is possible. I do not understand in the real world how after repeated use the threads movement is not smooth.

                                

                              Is it a must the depth of the cutting profile is half of the pitch dimension?

                               

                              I couldn’t understand why 1.11 is replaced with 1.5, because it is not changing the shape of the cutting profile, only dimension location changed. It is related to personal preference only. 

                                • Re: Thread Cutting
                                  Dan Pihlaja

                                  Screw thread - Wikipedia

                                  This is a pretty good resource on threads.....there are others, but this one is easy to get to.

                                  • Re: Thread Cutting
                                    J. Mather

                                    Maha Nadarasa wrote:

                                     

                                    ....

                                     

                                    I couldn’t understand why 1.11 is replaced with 1.5, because it is not changing the shape of the cutting profile, only dimension location changed. It is related to personal preference only.

                                    If you had not been given 1.11 - what logic would give you that number?

                                     

                                    You are following YouTube videos where information (often incorrect) is "spoon-fed".

                                    How will you make logical design decisions when you are designing new products/processes/tooling/machinery?

                                    That is where you need to start applying what you have learned.

                                    Rather than blindly reproducing - make a decision to use obvious symmetry when appropriate.  Question dimensions that do not have obvious logical explanation.

                                    Grasshopper - it is time to pluck the pebble from the instructors hand.

                                      • Re: Thread Cutting
                                        Maha Nadarasa

                                        YouTube videos are merely source of information. There are ample unknown information for a novice. It may be incorrect because there is no quality control over YouTube information. Even though why worry because there are experts in forum to double check the information.

                                         

                                        Some YouTube model are without drawings. I have requested such demonstrators to produce the drawing before developing a model then only I can sketch according to drawing and check with demonstrators work. This is the way we do in the SW class.       

                                      • Re: Thread Cutting
                                        Dan Pihlaja

                                        ISO metric screw thread - Wikipedia

                                         

                                        Metric Thread Size and Tolerance Calculator

                                         

                                        If you look at this link, you will see the calculations for ISO metric screw threads, which are the most common form of thread.

                                  • Re: Thread Cutting
                                    Maha Nadarasa

                                    Thank you for the help.