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A rather strange tap, NOT what I expected

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  • A rather strange tap, NOT what I expected

    I picked this out of the drawer in the shop, but something seemed wrong about it. Then I spotted the problem, which was certainly not what I would expect to see.

    4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

    Keep eye on ball.
    Hashim Khan

    Everything not impossible is compulsory

    "There's no pleasing these serpents"......Lewis Carroll

  • #2
    !/4-18 NPT pipe thread is common, but that seems to be a straight tap.

    https://military-fasteners.com/screw...1821bh031c125n

    https://www.tractorbynet.com/forums/...d-machine.html

    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

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    • #3
      It is a straight tap, and is not in the standard thread series. Probably if I knew what the "SB" was, I would not be so surprised. At 1/4", it ain't "structural bolt" as far as I know.
      4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

      Keep eye on ball.
      Hashim Khan

      Everything not impossible is compulsory

      "There's no pleasing these serpents"......Lewis Carroll

      Comment


      • #4
        Well, i found out that parallel pipe threads do actually exist, in that size too:
        https://www.gewinde-normen.de/en/npsf-pipe-thread.html

        But, doubt thats what that tap is

        Comment


        • #5
          Originally posted by epicfail48 View Post
          Well, i found out that parallel pipe threads do actually exist, in that size too:
          https://www.gewinde-normen.de/en/npsf-pipe-thread.html

          But, doubt thats what that tap is
          You are correct. Ain't no way....

          This tap is actually 1/4" diameter..... not "for 1/4 inch pipe", which would be a lot larger.

          I did not put in a size reference, sorry, I guess I figured the size of the markings would indicate the diameter, but that is not necessarily a good indication.

          As near as I can see, it actually is for 1/4-18 threads. Never heard of that size, and I have a whole compartmented tray of odd size taps and dies used on strange bits of machinery, old machines, etc..
          Last edited by J Tiers; 12-29-2020, 01:18 AM.
          4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

          Keep eye on ball.
          Hashim Khan

          Everything not impossible is compulsory

          "There's no pleasing these serpents"......Lewis Carroll

          Comment


          • #6
            S.B. might be Stove Bolt. Definitely not a common size, must be pretty old.

            Comment


            • #7
              Standard British , I bet....... but now to figure out ..US it BSF or BFC ? What does it Mic at ?
              am I the only one that has the DORMER TAP handbook ?
              and tapped hundreds of Straight pipe threads ?

              Dang it BsP 1/4 is 19 tpi..
              Last edited by 754; 12-29-2020, 03:51 AM.

              Comment


              • #8
                The 1/4" diameter is the one where I have seen the most non-standard threads. I once saw 1/4-23, would you believe. So 1/4-18 is no surprise to me: just one more to add to the mental collection.

                The biggest thing that jumps out to me is the way the thread tapers off from the bottom at the shank end. And the flats at the top of the thread get smaller there. Does the diameter increase in that section? How was that made? Did they roll the thread before cutting the flutes? But that does not explain the increasing fill in the valleys.

                Was it cut with a die? Only that seems to make any sense.

                ?????
                Last edited by Paul Alciatore; 12-29-2020, 02:25 AM.
                Paul A.
                SE Texas

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

                Comment


                • #9
                  Taps have been die cut (and dies cut with a tap) as well as being ground, cut, and maybe even rolled. It does look like it was die cut, and then the flutes cut.
                  4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

                  Keep eye on ball.
                  Hashim Khan

                  Everything not impossible is compulsory

                  "There's no pleasing these serpents"......Lewis Carroll

                  Comment


                  • #10
                    Land Rover track rods tap... Tracy tools sells them..
                    looked at this.. Click image for larger version

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                    Last edited by 754; 12-29-2020, 02:43 AM.

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                    • #11
                      OK, on a land rover, might be any damn thing...... they seem to have gone for the "creativity points" from what I am told. Don't have one, thought about having one a while back.

                      Land rover forum says it is 11/16-16 though......
                      Last edited by J Tiers; 12-29-2020, 02:37 AM.
                      4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942

                      Keep eye on ball.
                      Hashim Khan

                      Everything not impossible is compulsory

                      "There's no pleasing these serpents"......Lewis Carroll

                      Comment


                      • #12
                        The tractorbynet discussion linked above says the 1/4-18 screws were used on some aluminum windows. And the other link shows some military bolts of that size.
                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

                        Comment


                        • #13
                          Travers sells them under special taps. $17.90
                          You may only view thumbnails in this gallery. This gallery has 1 photos.

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                          • #14
                            OK, I can read what it says on the front, but theres something else written down the side. What does that say? It looks to have made pretty roughly.
                            'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

                            Comment


                            • #15
                              As already mentioned, pipe threads are different from ordinary threads, as the size is the bore of the pipe, not the od of the thread. Over the years there have been all sorts of odd sizes made for specific jobs and not intended at the time to cause confusion 70 years later.

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