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What type of bolt is this?

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  • What type of bolt is this?

    Somebody dragged this into the shop the other day, and after studying it closely, a severe case of head scratching broke out. It appears to be 10mm with the fine thread 1.25 and the "spiral" thread about 11TPI. What is strange is that the fine thread is right handed, while the spiral is left handed. Anybody have any ideas?

    Wayne

  • #2
    Anchor bolt, where its driven through a beam Left handedly, then some thing is hung on it and a nut used to secure it.

    Dave
    Just south of Sudspumpwater UK

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    • #3
      That's a honda civic 1.6 liter cylinder head expansion bolt... That's my story and I am stickin to it...

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      • #4
        It is a head bolt for sure.

        Cheers
        Mac.

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        • #5
          It is a black bolt....Maybe even a metal one as well..
          Precision takes time.

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          • #6
            Quote by motorcyclemac

            [It is a head bolt for sure.]

            Yes quite right, Frankensteins monster had two through his neck to keep his head from dropping off. One with a left hand thread and one with a right hand one.
            MBB

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            • #7
              honda gold wing motor cycle engies used bolts like this also think they were head bolts grt

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              • #8
                Is the "spiral thread" a single or double lead?

                Roger
                Any products mentioned in my posts have been endorsed by their manufacturer.

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                • #9
                  It is a head bolt, used by many manufacturers. See, for example:
                  http://www.yiparts.com/Part/es/HFRCF

                  VW p/n. I've hear that the LH threaded section is to allow the thinning of the "neck" of the bolt to allow increased clamping "springiness" or pressure while still allowing for high torque during installation without unwanted deformation (there was a debate about why they thin out the necks of head bolts about a year ago either here or on PM, if you want to read about what a thin neck purports to do). I also heard that it was to aid in lubrication for some reason. Don't know if either is true. I've never personally worked on an engine that used them.

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                  • #10
                    It appears to be a single lead and after the wire brush I'd have to say it is a black bolt. The letter T is on the head, if that's any help.
                    Wayne

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                    • #11
                      I'm with A.K. on this one, have taken out lots of honda head bolts in the past.

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                      • #12
                        Given the structure of the bolt, I could certainly see it falling in the head bolt class, but how does one engage threads in one direction, and then the opposite..... especially into a blind hole such as a cylinder head? The major dia. of both threads are pretty close....388 for the fine and .390 for the spiral.
                        Wayne

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                        • #13
                          The head bolt will only engage threads on the end of the bolt. The reverse threads are not meant to engage thread area, they are for stretch and stress tension.
                          It's only ink and paper

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                          • #14
                            its a differential screw bolt, its use is unknown but fixing dissimilars seems optimistic
                            happy November to all
                            mark

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                            • #15
                              Looks like a nifty idea to get head bolts out of ali cylinder heads when they corrode in place!

                              Peter
                              I have tools I don't know how to use!!

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