17/64" bolt size?

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  • November 21, 2017 at 1:51 am #8713
    Buccaneer
    Participant

      US Member

      The Johnson Model 100 I’m working on is missing one correct
      size bolt that holds the cylinder onto the crankcase.

      It’s OD is 17/64" in the drill gauge……. one size bigger than 1/4".
      A 1/4" nut will barely start on these bolts, but only go about
      a 1/4 turn.

      These bolts appear to be 20 tpi as a 1/4" bolt.

      A 1/4" bolt screws in the hole okay, but is way too loose.

      I can find no such thing as a 17/64" bolt.
      Am I hallucinating?
      Thanks.

      Prepare to be boarded!

      November 21, 2017 at 2:53 am #67731
      Mumbles
      Participant

        Singer sewing machines used 17/64 x 28 in their products but yours with 20 TPI is really odd! You have to remember that manufacturers back then before standardization could make their fasteners any size or pitch they wanted so maybe that’s what the Johnson Bros did here. You could always drill it out and insert a 1/4 x 20 Helicoil. No one would know.

        November 21, 2017 at 3:27 am #67732
        green-thumbs
        Participant

          US Member - 2 Years

          There are 2 common 1/4" and 2 not so common
          coarse 20tpi, intermediate 24 tpi fine 28 tpi and super fine 32tpi
          It may be the 1/4"x 24tpi is what you have. I have a tap in that size that is too big for
          1/4" drill gauge and a loose fit in 17/64" hole.
          Making a replacement from a sample would be basic lathe task
          Finding a correct screw may be possible…others here may know where to start.
          Louis

          November 21, 2017 at 4:07 am #67735
          Buccaneer
          Participant

            US Member

            Thanks for the replies. When I held the threads of a 1/4" x 20
            bolt next to the bolt in question, the pitches seem to match,
            but I’ll put a thread gauge on it tomorrow to make sure.
            I looked on the "Net" for obscure bolts sizes, but really
            didn’t find much!

            Prepare to be boarded!

            November 21, 2017 at 4:21 am #67736
            The Boat House
            Participant

              Johnson used the 14" x 24 thread in several places
              on there motors. Check the drain screw in
              the carburetor. I think you’ll find its the same.

              November 21, 2017 at 8:12 am #67740
              Mumbles
              Participant

                Johnson also used 14 X 24 machine screws to secure the rope sheaves on early motors. With a diameter of 0.242", they are slightly smaller than a 1/4" screw.

                November 21, 2017 at 12:58 pm #67745
                Buccaneer
                Participant

                  US Member

                  I just went thru the odd size bolts on the rope sheave routine,
                  and had to make an adapter plate to attach the plate to the
                  flywheel with the rope sheave bolts, then attach my puller
                  to the plate with long 1/4" bolts. Fun, lol.

                  Prepare to be boarded!

                  November 21, 2017 at 4:17 pm #67754
                  amuller
                  Participant

                    This subject was chewed on a few weeks ago here: viewtopic.php?f=2&t=14362

                    Conclusion is that you are most likely dealing with #14 x 24 fasteners. This is a long-obsolete size not mentioned in most current thread size tables.

                    November 21, 2017 at 6:40 pm #67760
                    Buccaneer
                    Participant

                      US Member

                      I brought up that subject matter regarding the bolts on the
                      flywheel, but the bolts in question in this subject are
                      "bigger" than 1/4", not smaller.
                      Just going to go out to the garage now and think about
                      it some more. I got roped into fixing the sweet potatoes
                      and cranberries for Turkey day, so have bee slaving the
                      the kitchen all morning, lol.

                      Prepare to be boarded!

                      November 22, 2017 at 12:18 am #67775
                      punchbug
                      Participant

                        It is possible that it is a Metric bolt. It seems odd that they would use that odd size on one place. It may have been stripped out and the person who repaired the bolt hole went to a comparable metric bolt. It could very well be a m6x1 metric.

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