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3/16" 28 TPI screw, why so hard to find?

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  • 3/16" 28 TPI screw, why so hard to find?

    I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI but they seem very hard to find. I would even go up to 6mm and retap but there are inserts ('helicoils'?) in the holes.

    I am in New Zealand and do not relish the thought of US$50 to courier a handful across the blue Pacific.

  • #2
    Thats a real odd size !
    the closest I know is a British Standard Brass Thread at 26 TPI for a 3/16" thread
    for Metric you would need a 4.5-.9 configuration which is nothing I have ever seen
    Its always possible it is a custom thread by the machine maker ??
    Rich
    Green Bay, WI

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    • #3
      Can you cut 28 tpi?

      If so, then you can make them. The major diameter has nothing particular to do with the TPI.
      CNC machines only go through the motions.

      Ideas expressed may be mine, or from anyone else in the universe.
      Not responsible for clerical errors. Or those made by lay people either.
      Number formats and units may be chosen at random depending on what day it is.
      I reserve the right to use a number system with any integer base without prior notice.
      Generalizations are understood to be "often" true, but not true in every case.

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      • #4
        #10-28 would be very odd and not something on the shelf anyway. What do the screws come off of?
        I just need one more tool,just one!

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        • #5
          Originally posted by The Artful Bodger View Post
          I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI...
          Almost certainly incorrect. Much more likely either 5mm or #10. Where was the "something" manufactured?
          12" x 35" Logan 2557V lathe
          Index "Super 55" mill
          18" Vectrax vertical bandsaw
          7" x 10" Vectrax mitering bandsaw
          24" State disc sander

          Comment


          • #6
            I have one screw that I think was original and it appears to be stainless steel. This part is a radar rotator from a ship's masthead but I am using it for something else so stainless is not required.

            In theory I should be able to cut 28 tpi as I am sure the required gears will be in my lathe kit, I am thinking of starting with 6mm screws which I think will have enough diameter once I turn the threads off.

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            • #7
              Originally posted by ezduzit View Post

              Almost certainly incorrect. Much more likely either 5mm or #10. Where was the "something" manufactured?
              Close to 5mm but the pitch would be 0.9 mm, possible but not likely.

              #10 just tells me it is 3/16". I see that 10-28 is listed on some sites but they are too far away for me to access.

              The ship the rotator came from was I believe Taiwanese and the electric motor shows Asian script so probably Japanese or Chinese manufacture.

              Other sizes of screws match imperial threads.
              Last edited by The Artful Bodger; 08-29-2022, 02:33 AM.

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              • #8
                Originally posted by The Artful Bodger View Post
                ...#10 just tells me it is 3/16"...
                No. It is 0.190"
                12" x 35" Logan 2557V lathe
                Index "Super 55" mill
                18" Vectrax vertical bandsaw
                7" x 10" Vectrax mitering bandsaw
                24" State disc sander

                Comment


                • #9
                  That sounds like an Aeronautical Standard Machine Screw. Cessna used them as well as others.

                  Also this: Screw for Sharps Tang Sight
                  , #10-28 thread, bright steel to mount Sharps tang sight. These screws have a 5/16" diameter head, a overall length of .42", and threaded shaft of .29".



                  Also: Lincoln Products 3/8" x 10/28" Brass Bibb Screws

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                  • #10
                    Wow, the Apple of machine screws! Actually they would probably do 27.3 turns so people couldn't even make them easily...

                    Comment


                    • #11
                      Number 10-28 seems to be part of the obsolete ASME (pre-UN) thread series.

                      I found some references to the thread being used in Juki sewing machines. See:



                      Put "3/16-28 screw juki" into Google and there are numerous hits, in different lengths. You would have to check if they ship to your place.

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                      • #12
                        Thanks, there may be something useful in those responses.
                        John

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                        • #13
                          Why couldn't they be shipped via the post office? Does New Zealand add some astronomical charge above US postal rates? Any US company could ship them to anywhere in the world starting for under US$15.

                          Ship globally with USPS. Compare international mailing and shipping rates and delivery times from overnight to 6-10 business days.




                          Originally posted by The Artful Bodger View Post
                          I am working on something that requires twelve screws that as far as I can tell are 3/16" 28TPI but they seem very hard to find. I would even go up to 6mm and retap but there are inserts ('helicoils'?) in the holes.

                          I am in New Zealand and do not relish the thought of US$50 to courier a handful across the blue Pacific.
                          Paul A.
                          SE Texas

                          And if you look REAL close at an analog signal,
                          You will find that it has discrete steps.

                          Comment


                          • #14
                            Regardless of the postage questions there seems to be very few online sources in the US for what I seek.

                            Comment


                            • #15
                              M5 x 1.0

                              -Doozer
                              DZER

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