The world of model and hobby engineering

Subscribe
The Modelling Hub Logo

The world of model and hobby engineering

Subscribe
Buy Latest Issue

Forums

Help

Register

Log in

2 start thread

Advert
New Replies
Report Bug
Help/FAQs

2 start thread

Home › Forums › Beginners questions › 2 start thread

Viewing 6 posts - 1 through 6 (of 6 total)
  • Author
    Posts
  • 22 July 2018 at 14:38 #363357
    Simon Williams 3
    Participant
      @simonwilliams3

      Hello all, cor ain't it 'ot!

      I have recently found myself repairing an exhibition stand, where the flat panels have 16 mm rods each sides to hold them together. I discovered that the thread I thought was M8 in each rod was actually 8 mm OD, but was two start. So the thread pitch is actually 2.5 mm not 1.25 mm.

      Which led me to wonder how such things are specified. The thread pitch measured with a thread gauge is 1.25 mm, but would I be right in supposing that, if I needed to specify such a thing to a professional turner I ought to call it "M8 x 2.5 pitch 2 start" (assumed symmetrical)?

      Look forward to hearing what the forum thinks?

      Thanks as always, Simon

      22 July 2018 at 14:38 #9264
      Simon Williams 3
      Participant
        @simonwilliams3

        What’s the teminology?

        22 July 2018 at 15:20 #363363
        HOWARDT
        Participant
          @howardt

          You are right, thread diameter x pitch (or lead) of thread and number of starts. I have used multi-start threads in designs over the years but most have been buttress or acme and in larger sizes.

          22 July 2018 at 15:24 #363364
          richardandtracy
          Participant
            @richardandtracy

            On my pen making have up to 5 starts, and that's just the way to specify it.

            Regards

            Richard.

            22 July 2018 at 20:27 #363401
            Pete Rimmer
            Participant
              @peterimmer30576
              Posted by Simon Williams 3 on 22/07/2018 14:38:15:

              Hello all, cor ain't it 'ot!

              I have recently found myself repairing an exhibition stand, where the flat panels have 16 mm rods each sides to hold them together. I discovered that the thread I thought was M8 in each rod was actually 8 mm OD, but was two start. So the thread pitch is actually 2.5 mm not 1.25 mm.

              Which led me to wonder how such things are specified. The thread pitch measured with a thread gauge is 1.25 mm, but would I be right in supposing that, if I needed to specify such a thing to a professional turner I ought to call it "M8 x 2.5 pitch 2 start" (assumed symmetrical)?

              Look forward to hearing what the forum thinks?

              Thanks as always, Simon

              You're nearly right. The pitch is still 1.25mm, but the LEAD is 2.5mm If you specify 'Thread 8mm, 2.5mm pitch, 2-start you'll' either get a 5mm lead thread or (more likely) an irate phonecall asking what it is you really want.

              So ask for 'Thread, 8mm OD, 2.5mm lead, 2-start'

              22 July 2018 at 21:23 #363407
              HOWARDT
              Participant
                @howardt

                Yes I agree with Pete, pitch is distance from one peak to the next, lead is distance travelled in one revolution.

              • Author
                Posts
              Viewing 6 posts - 1 through 6 (of 6 total)
              • Please log in to reply to this topic. Registering is free and easy using the links on the menu at the top of this page.

              Latest Replies
              Report Bug
              Code of Conduct
              Help & FAQs
              Advert

              Latest Replies

              Home › Forums › Beginners questions › Topics

              Viewing 25 topics - 1 through 25 (of 25 total)
              Viewing 25 topics - 1 through 25 (of 25 total)

              View full reply list.

              Advert

              Latest Issue

              Subscribe
              Buy Latest/Back Issues

              Newsletter Sign-up

              Latest Replies