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Sticking 3-wires for thread measuring??

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  • Sticking 3-wires for thread measuring??

    What's a simple trick to stick the 3 wires to the part, when measuring with a mic?
    Seeing as I don't have 4 arms.

  • #2
    GREASE, grease, grease


    • #3
      I set the mic a tad bigger than I expect and use my fingers to hold the wires as I slide the mic over them.

      My Web Site


      • #4
        Black (or pink) electrostatic foam works great, and no mess cleaning up the wires.
        "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."


        • #5
          Hate to sound(& be) stupid, but can someone explain how this works? Thanks!
          "Let me recommend the best medicine in the
          world: a long journey, at a mild season, through a pleasant
          country, in easy stages."
          ~ James Madison


          • #6
            I use a lump of modeling clay. Pressure from the mic will move the wires into the proper position and give an accurate reading.



            • #7
              Originally posted by flylo View Post
              Hate to sound(& be) stupid, but can someone explain how this works? Thanks!
              the grease or the three wire method?

              Here's a site that explains the three wire method:

              I remember some thread wires that were called "Flin Wires" (sp?). They were not accurate enough for Mil-Spec parts, but close enough for virtually everything else. Seem to remember a set had fewer wires than usual and it included a chart that made it easy to calculate the PD.

              The grease acts as stickum to hold the wires in place. Just hit the part with some electromotive or brake clean to remove the grease.


              • #8
                Grease to hold the wires on the work....or stick the wires in plasticine (modelling clay) are both things I've used. They reduce the frustration from a 12/10 to about an 8. The wire falls off the grease, the move and shift in the modelling clay..Arrg

                we should use thread wires all the time.....its only because they're a 8/10 on the miser scale that we don't

                I've got a way to reduce it to a 3. snip two pieces of bicycle inner tube maybe 3/8 wide and an inch long. Punch a 1/4 hole in the centre (mics in my experience are 1/4" anvils). with an exacto knife make two slides at each end.

                Slip the wires through the slits, two in one and one in the other and then the whole assemblies on the anvils. It works well. There is a commerical product out plastic that does the same but the price is just plan stupid


                • #9
                  Empty the chip pan BEFORE using the wires !!


                  • #10
                    Originally posted by lazlo View Post
                    Black (or pink) electrostatic foam works great, and no mess cleaning up the wires.
                    Probably the best (cheap) solution I've seen yet Have to try this next time when I'm making a thread that I have no gauge for.
                    Amount of experience is in direct proportion to the value of broken equipment.


                    • #11
                      The theory of the 3-wire system is fine but the application of it is or can be a PITA.

                      Using the 3-wire calculations and the known outside diameterof the part being threaded it is quite possible and practical too to get comparable results with either two or one of those wires. It just requires a bit of reasonably easy additional maths.

                      For those that are "worried" because for some reason I can't fathom or understand they think that "3-wire work" is "tenths work", I can tell you its notso - at all.

                      The Limits for thread pitch diameters are quite wide apart - see Machinery's Hand Book 27 page 1736 and onward (its a big table) Table 3 "Standard Series Selected Combinations Unified Screw Threads".

                      You should find most common UNF threads in there as it also includes the upper and lower limits for external and internal pitch diameters for Classes 2A and 2B.

                      Here is an example of the calculations for a 1/2- 13 - UNC - 3A external thread pitch diameter to be measured with "3-wires":


                      Notice that there is 0.005" (5 thou) difference in the limits ie what you measure with 3-wires and a micrometer - not "tenths" at all - just "thous".

                      Here it is graphically:

                      The best easiest and simplest way to measure external screw thread pitch diameters directly - and almost certainly the most accurate and repeatable way is to use a thread micrometer.

             and look for items 32370 32371 and 32372


                      • #12
                        I use tiny orthodontic rubber bands, one on each end of the wires to hold them in place. No mess, and they stay in place even if bumped accidentally. They come in a couple of sizes and can be had for the asking usually.


                        • #13
                          I'm in the grease camp. Simple as can be. But I will also agree, that you should put something under them when measuring. Sometimes you bump or move them getting the mic in place and they fall. So to save a lot of headache, place anything, cardboard, newspaper, whatever under the piece when measuring.


                          • #14
                            Use grease to stick wires in place. Clean w/ a wiper when done and putting away.. Grease residue on wires is a good thing. Less chance for rust.


                            • #15
                              I've always used a strip of 2" wide duct tape. Fold it in half while being careful not to completely stick the ends together. Cut one end in half and stick a thread wire in each of the halves and seal the tape around them. Stick the third thread wire in the other end. Then I write the wire size on the tape in permanent marker. Since I have been doing this, I have yet to lose a wire and they are easier to manage.