No announcement yet.

3 wire thread measuring

  • Filter
  • Time
  • Show
Clear All
new posts

  • #46
    Anything that does the job

    Thanks Paul - appreciated.

    Agreed re. removal of burrs etc. with the caveat that they may well cause more problems with "sizing" than removal of any of the OD. The "finger-rub" or "finger-nail scratch" tests are pretty good at picking-up many of these problems.

    Re. your question regarding hex etc. the short answer is that anything that can do the job will do the job. "Round" is easier. But even on hex key stock, providing you know the distance across the flats as well as the distance over the corners and can replicate them in the CAD drawing - it should do the job as most rolled/drawn hex stock will be very "regular" even if not "on-size". The "distance across the corners" - ie over the rounded corner can be sufficient if shown as "flats" instead of "rounded" as you will be measuring such that the micrometer will be tangent to any rounding on the corners. In fact only one "corner" is needed on the CAD drawing/file - the one that is being used for the micrometer setting/reading. The rest (5) "corners" can be shown just as "sharps" or "over-shoots" as it is only the two flats in contact with thread flanks/sides that count for thread contact. The two that form the "point" where the micrometer setting is represented need to be accurate as well.

    "Rounds" will include the shanks of drill bits if their condition is OK. Any good "round/s" in the shop a the time will do. The size can be got with a micrometer and incorporated into the CAD file/drawing.

    There are far too many chances of error with the "3-wire" method - from reading tables or "working things out" from formulae etc. This is in addition to actually getting the measurements correctly, accurately and repeatably. Its pretty well the Machinist's equivalent of herding cats or pinning jello/jelly to the wall - which are easier!!


    • #47
      3 Wire threads

      I can cut threads- to suit. I can do geometry or enough to do Euclid or Pythagaras and the proofs but I cannot do CAD. I simply got programs with so many fancy things that my old head reeled.
      What dead easy program deals with drawing match boxes with dimensions and none of this fancy stuff which can come later?

      Sorry fellas to cut across your discussion. This is a chance




      • #48

        with your having dealt with many Cads and Bounders in your time, I thought it would have been a cinch.


        • #49
          £ Wire Thread

          Ah Tiff,
          You mean the 'Sands of the Desert is sodden red
          Red with the wreck of a square which broke
          The gatlings jamed, and the colonel dead
          the regiment blinded with dust and smoke
          and the voice of the schoolboy rallies the ranks
          'Play up, play up and play the game'

          But isn't this the other posting? What's an Air Attache- by the way.
          Got me one, got a bit fat since he flew Tornados- you know?
          Hmmm? Do you think that I could be a Cad? For once, I feel like pulling rank, or the Old Boy's Act or whatever one does.

          A Bounder goes over the top whilst a Yorker goes under. Nelson sunk the French Fleet with the latter.I really am pi55ed off!




          • #50
            Originally posted by Paul Alciatore

            While reading this, I had a thought. For a 60 degree thread, I wonder if hex stock would be better than round wires? You would have a line of contact instead of a point so there would be less chance of pressing it into the surface. Of course, you would need precision hex stock, not just any old allen wrenches.
            Already done...... thread triangles. They are not pointy, but are actually more-or-less hex, with the points knocked off to avoid issues relative to minor diameter.
            CNC machines only go through the motions