Measuring a pitch

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  • Measuring a pitch

    I've been asked to measure a pitch of a thread. I'm not sure how to do that, or if it's even possible?

  • #2
    You are able to set pitch in an Auto Cylinder

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    • #3
      I think nano is asking about the pitch diameter, my opinion waste of time on CMM. Molding and Comparator on ID or cut the part. Three wires and OD mic. on OD.
      (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
      They say "Nobody's Perfect." I must be Nobody.

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      • #4
        I don't need to set the pitch, nor i need to measure a pitch diameter.

        I need to measure a 1.65 mm pitch of a single thread that's only about 300° around.

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        • KIRBSTER269
          KIRBSTER269 commented
          Editing a comment
          Oh the length? or you need to know if the 1.65 mm pitch is correct with not even a complete circle?
          Last edited by KIRBSTER269; 05-16-2018, 12:56 PM.

      • #5
        Pitch diameter is the diameter in which the threads engage, the function diameter.
        Thread pitch is the distance between threads.
        Thread length/depth is the functional length along the threaded feature's axis.

        Which one do you want measured?

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        • #6
          Yes, I need to know if an incomplete thread has correct pitch of 1.65 mm.

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          • #7
            Originally posted by louisd View Post
            pitch diameter is the diameter in which the threads engage, the function diameter.
            Thread pitch is the distance between threads.
            Thread length/depth is the functional length along the threaded feature's axis.

            Which one do you want measured?
            i need thread pitch

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            • Don Meredith
              Don Meredith commented
              Editing a comment
              Thread pitch gage?

            • Nano Vujkovic
              Nano Vujkovic commented
              Editing a comment
              Over one incomplete thread?

          • #8
            Measure a scan line along one edge of the threads (line will be parallel to axis of Bore/boss).
            Use an assignment to extract the max point, which would be the minor diameter of the thread (if it's a bore).
            repeat same line and same assignment 180° from the first one.
            The distance (along axis) between max points will be 1/2 your measured thread pitch. double that result and output your data.
            Last edited by louisd; 05-16-2018, 01:31 PM.

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            • KIRBSTER269
              KIRBSTER269 commented
              Editing a comment
              He has one thread and it isn't even 360 degrees

            • Nano Vujkovic
              Nano Vujkovic commented
              Editing a comment
              I'm not sure what you mean by edge of the thread

          • #9
            thread pitch.png

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            • Nano Vujkovic
              Nano Vujkovic commented
              Editing a comment
              I think i understand, but i only have one incomplete thread.

            • louisd
              louisd commented
              Editing a comment
              Yes, but that one incomplete thread is more than 180 degrees, you said it was 300 degrees. You only need 180 degrees for this method, so get to it! lol!

          • #10
            This could be done on an optical comparator rather easily on an od thread, and if its an id thread then mold it with repro-rubber.

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            • #11
              This thread was started at 11:07 A.M. The right answer was at 11:30 A.M. Part could have been checked and done with, at 11:45 A.M. Here it is 2:05 P.M. and we still don't know if the part is good or not
              (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
              They say "Nobody's Perfect." I must be Nobody.

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              • #12
                I have a lot of parts to check and we cannot cut all of them, the parts are PEEK and we don't have anything in house we can mold with without destroying the material.

                The upper thread is more flat than the pitch, the bottom of the thread has full 1.65 mm pitch. Also the thread is more like ACME thread, the minor diameter has a flat, not a point and i cannot get just one max point.

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                • louisd
                  louisd commented
                  Editing a comment
                  well pick one edge then, or midpoint the intersects of the acme thread angle to minor diameter flats. all I hear are excuses. I'd have that crap done already :-S

                • louisd
                  louisd commented
                  Editing a comment
                  if you only have 90° of fully formed thread, do exactly what I described, but with a span of 90° instead of 180, and x4 that data.

                • Nano Vujkovic
                  Nano Vujkovic commented
                  Editing a comment
                  Thank you louisd for all your input, especially the one where you bash me, lol. Maybe all i have are excuses, but you don't have to get frustrated about it. You don't work with me.

              • #13
                Stick the male end in and see if it works?

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                • Nano Vujkovic
                  Nano Vujkovic commented
                  Editing a comment
                  Wouldn't that be nice

              • #14
                I don't think my description was good, i'll try again. One side of the thread is almost flat across and it has very little pitch, the other side is curved with full pitch. The minor Ø is 3 mm, so everything is very tiny, the whole part is 13.5 mm. I've tried measuring various feature (lines, circles, planes, cylinders...), extracting min, max data, intersecting them, but i cant get anything consistent or even close to nominal.

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                • InspectorJester
                  InspectorJester commented
                  Editing a comment
                  Problem solved!

                • acgarcia
                  acgarcia commented
                  Editing a comment
                  CMM are not universal machines. I'm told to do things all the time by non-cmm users and I get Hex tech support involved to back me up. If I don't know how to do something hex can help out or they say it can't be done like that. Our first CMM was bought with the intent of measuring threads and replacing threaded gages. App engineer showed up for our first part program and said guess what, CMMs can't measure threads. My bosses head nearly exploded. Management hates it when the expensive beeping machine has limitations.

                • KIRBSTER269
                  KIRBSTER269 commented
                  Editing a comment
                  I apologize nano. I meant if they insist, your knucklehead bosses

              • #15
                Same here Nano Vujkovic I've always been told CMM cannot measure threads. I tried every thing I can think of to try and measure some threads. We tried measuring these large acme threads for the pitch diameter and I always got inconsistent results. We even paid a contractor for a program to check these threads and the probe would crash into the part most of the time and give false reports. I ended up not using the program. We even sent a part to Hexagon and they used a scanning probe but the results didn't match. For example the report said the threads were out of tolerance but go no go gages we used on them worked as intended. Go gage went, no go didn't go. Who's right and who's wrong?

                You would think that out of all the CMM software's and machines out there, that someone would have figured out how to accurately measure threads.

                Mitutoyo has a contour machine that uses blade like styli to measure contours and threads. We looked into buying one but never did. We still use threads gages.

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