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Botched helicoil repair

Discussion in 'The Garage' started by Mitch81special, Apr 8, 2021.

  1. Hi everybody, so iv got myself in a pickle. I was attempting a helicoil repair a valve cover stud. I neglected to use a non-tapered tap and when I installed the helicoil it followed the now tapered threads and essentially I have a tapered helicoil. So I'm thinking if i can remove that helicoil without damaging the new threads then i can grind the taper off my tap, finsh the job and reinstall a new helicoil. My question is how do I go about removing the helicoil? Iv seen the special arrow head shaped tool that grabs and twists them out but I'm worried that this coil is so tight in there because of the taper that might not work. Also seen a video of a guy just picking one thread out then peeling the whole thing out like a slinky. Any tips greatly appreciated.
  2. Machine

    Machine Race the wind Top Contributor

    Yes, unwind it out like a slinky lol.
    Tap deeper of course and use a new helicoil.
    You haven't likely damaged anything too bad yet
    TwoManyXS1Bs, kshansen and nj1639 like this.
  3. Raymond

    Raymond XS650 rider & fettler XS650.com Supporter Top Contributor

    No guarantees, coz I've not done it meself, but when I took a Triumph rocker box to an engineer to ask about a Helicoil, he just grabbed the end of the insert with a pair of needle-nose pliers and pulled it out. The insert kind of unwound as he pulled - probably what you meant by like a slinky?

    I suppose you have the extra reassurance that you intend to re-tap the hole in any case . . .

    Edit - crossed in the post with Machine.
    gggGary likes this.
  4. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    I would try to grab one of the top threads with a pair of needle nose pliers and gently rotate CCW it should twist out if you're patient and gentle. I would then start over with a Timesert or EZ-LOK insert.
  5. RC4MAN

    RC4MAN XS650 Addict

    I've done it both ways, depends on how deep you've threaded the coil in.
    Technically you're supposed to turn it in till the end of the coil is fully engaged in the tapped hole which makes it more difficult to peel the coil out.
    If you have a scribe or other sharp pointed tool you may be able to get the end picked out enough to grab with needle nose pliers.
    The "arrow" pointed tool also works, you just need to be careful to place it so that the edge is as far from the coil end as possible, especially in softer material like aluminum. If not you might cause the coil end to bite into the base metal and raise a burr which will make it difficult to turn the coil out. It also helps if when you insert the tool into the coil you rock it back and forth so the tool edge cuts into the coil a bit for a better bite before you try and turn it out
    kshansen likes this.
  6. Max Midnight

    Max Midnight XS650 Addict

    You would normally use a taper tap to start with and if required follow that with a bottoming tap where the cutting part goes to the bottom of the tool.
    This will cut the tread to within the last 1 to 2 turns of the thread.
  7. nj1639

    nj1639 Paleo-simplistic Top Contributor

    I've done a couple on the valve covers using a standard tapered bit. First I probe the hole for depth and then mark the drill bit with a bit of tape so as to not drill deeper, but consider the end taper in your measurements as the insert "no go" area and drill accordingly. The heli-coil insert is a fraction of the depth and it just needs to be below the finished surface. Once set to the desired depth the tab is broken off allowing the bolt to travel past the coil.
    Mistakes can be unwound as stated above.
    RC4MAN likes this.
  8. bosco659

    bosco659 XS650 Junkie XS650.com Supporter

    With some patience you should be able to get it out. Maybe shoot some oil in the hole to keep things moving. I’m a bit puzzled about the tapered tap. All my helicoil taps are more like bottoming taps meaning they are fairly square shouldered at the end. Good luck with the extraction.
    Last edited: Apr 8, 2021
    arcticXS and Raymond like this.
  9. cra-z1

    cra-z1 XS650 Junkie Top Contributor

    I would go with the Timesert
  10. Mailman

    Mailman Hardly a Guru Top Contributor

    Ok, I’ll bite. What is the thumbnail comparison in these products?
    Jim likes this.
  11. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Helicoil is square cross section wire, wound to shape. Timesert is a solid bushing.

    RustiePyles and Mailman like this.
  12. Mailman

    Mailman Hardly a Guru Top Contributor

    Ah so, thus a stronger repair.
    Jim and RustiePyles like this.
  13. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    There is of course a cost difference between the two as well.
    RC4MAN and Mailman like this.
  14. 5twins

    5twins XS650 Guru Top Contributor

    They do make Heli-Coil bottoming taps. I have the M6 sized one and have used it several times, including on a valve cover stud repair.
  15. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    Yep, also called blind taps or gun taps
  16. Jan_P

    Jan_P XS650 Junkie

    Is there a problem here at all ? .. Am I a bit far out here perhaps ??
    Perhaps something I have Misunderstood.
    There are conical threads at may places piping fex
    As i Understand it the pre tap has been used and not the bottom tap making the bottom end of the hole conical
    Not fully threaded
    But if you insert the stud wont it bottom out against the conical hole and and sit tight .
    If careful and keeping the torque in check
    The pin shall not be removed ... Or ??
    and if worried perhaps making the pin conical with an angle grinder.
    This depends on how it looks and how far in the pin goes and the H coil is in
    pin sticking out.and so on
    as a rule of thumb the same Thread length as the nut can be good.
    And this being a place where the pin never shall be removed
    And if careful tightening and loosening the cover perhaps it is OK
    nj1639 likes this.
  17. Thanks for the input everyone. I managed to successfully remove the helicoil by peeling it out. I then grinded my tap to a bottoming tap and finished tapping the hole.
    Some comments make me think people think this stud hole is deeper than it is. It is only as deep as the post and the helicoil isn't much shorter than that. And I was unsure about drilling any deeper than the factory hole. 20210408_162252.jpg
    cra-z1, timbeck, RC4MAN and 5 others like this.
  18. bosco659

    bosco659 XS650 Junkie XS650.com Supporter

    Glad you got it fixed up!
    Raymond and Mailman like this.

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