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  • Thread measuring triangles

    Does anyone use the triangles for cutting threads? Purchased a set today the chart they sent with them was a photocopy and they didn't get the whole chart, it's missing the formula for the larger sizes. I can probably work it out by comparing dimensions of other threads on the chart.Can someone help me out?
    Thanks
    Gary

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  • #2
    Who made them?

    I have a set from Elisha Penniman Co.

    The dimension tables should vary depending on the size of the triangles, so just any table won't necessarily work.

    But if you have a set like mine, I can copy the info at larger scale for you.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #3
      J Tiers
      I'm not sure who made them, I have them at work. Your right the specs. would be different depending on size. Never thought about different sized triangles. I think the container had the letters SPI on it, will have to check on that and let you know.
      Thanks
      Gary

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      • #4
        SPI = Swiss Precision Instruments Seems to be an importer/wholesaler of stuff from various countries. MSC carries them. Website at http://www.swissprec.com

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        Leigh
        Leigh
        The entire content of this post is copyright by, and is the sole property of, the author. No assignment
        of title nor right of publication shall ensue from presentation of this material on any computer site.

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        • #5
          "I think the container had the letters SPI on it..."

          SPI = Swiss Precision Instruments. Despite the name, the company is headquartered in Singapore, and has a plant in Thailand. Good quality products, from my experience. Website (very little info) at http://www.swiss-precision-ind.com.sg

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          Leigh
          Leigh
          The entire content of this post is copyright by, and is the sole property of, the author. No assignment
          of title nor right of publication shall ensue from presentation of this material on any computer site.

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          • #6
            Hi Gary

            Just a note of caution on using those triangles: While o.k. in theory, their accuracy is totally dependent on thread form, so unless you have a perfect 60 degree cutting tool (e.g. carbide insert) the chance of meaningful measurement using them is absolutely zilch. If the cut angle is slightly too wide, the triangle faces will contact nearer the root diameter; if it’s a bit too narrow, they’ll hit somewhere closer to the major diameter, in either case not the critical pitch diameter you’re shooting for. I bought myself a set of those puppys several years ago before understanding their limitations vis-a-vis hand-ground HSS tooling and now they just sit collecting dust. For my money, the only way to make accurate pitch diameter measurements is over wires. And, btw, the same limitations apply to thread measuring mics, as well, and for exactly the same reason.

            Hope this helps.

            Kind regards,

            Jack


            [This message has been edited by Jack Burns (edited 12-02-2005).]

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            • #7
              Just a note of caution on using those triangles: While perhaps o.k. in theory, their accuracy is totally dependent on thread form, so unless you have a perfect 60 degree cutting tool (e.g. carbide insert) the chance of meaningful measurement using them is absolutely zilch.

              While I do agree that the thread form needs to be accurate to get accurate pitch measurements, I wouldn't let using hss ground tooling stop me from using them. If I am going to take the time to check pitch diameter of a thread I think I would take the time to use a properly ground tool. It's not rocket science and with a little practice they are not that hard to grind. Using a carbide insert doesn't guarantee perfect threads either because it still has to be set up square to the work which once again throws in room for operator error. I have a set and would rather use them over thread wires any day but that is just my preference. At work we have a 0 to 6in. set of pitch mics and I wouldn't trade them for anything. They are fast and easy to use and very accurate. By the way, wouldn't thread wires give an inaccurate reading to if the tool geometry was wrong
              Jonathan P.

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              • #8
                If you have purchased something and it is incomplete in some respect making is less than useable, your first line of defense is the manufacturer or vendor.

                Let them know of the problem, and ask where the returned merchandise should be sent, and how quickly a proper replacement will be sent, or when the refund will be received.
                Jim H.

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                • #9
                  Japcas:

                  I think the same can be said of thread wires, unless you use two sizes of wire.... and detect the form error.

                  The contact spot may be convex or concave, and give wrong readings even with wires.

                  All depend on form being right, even thread gages. And of course, that isn''t a huge problem, as form SHOULD be right.

                  But your point is that the form may be wrong, and read right...... i.e. wrong depth of thread, wrong form, right reading...... OK I'll buy that, but one set of wires won't necessarily find that either.

                  [This message has been edited by J Tiers (edited 12-02-2005).]
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Thanks to all for your replies. I understand what you all are saying about proper thread form and accuracy of the the measurements. I'm using carbide inserts so all I have to do is get it set up properly. I did a little playing with them yesterday measurements were corresponding with the chart. Will try them out soon.
                    Thanks
                    Gary




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