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DHi/bolt-extraction gurus

Discussion in 'Downhill & Freeride' started by - seb, Feb 17, 2009.

  1. - seb

    - seb Turbo Monkey

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    OK, I've managed to round off the dogbone bolt on my DHi. Not the one that bolts to the mainframe, the one that bolts to the eccentric. Is a 3mm head and although I kinda knew it was going to go and was careful to clean the head out before pushing any harder, and squirted some plus gas in from the other side etc etc, it still went.

    Buggered if I know how I'm going to sort it. Drilling it out wont be simple, I can't simply drill the head off, need to drill it out from the threads end if anything. Virtually impossible action to cut a slot into the head of it, even if I had a dremel (which I don't).

    Any ideas? Would an engineering place have this out for me in seconds using cunning tools/tactics that I don't have/know?

    (Eccentric hasn't been rebuilt in about a year, I figured it was time as I was stripping the bike down today. Sounds very gritty, but if I have to put the bike back together as it is I can probably live with it, hopefully new frame/bike time later this year anyway...)
     

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  2. ohio

    ohio The Fresno Kid

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    Can you get an extraction bit in there? With allen heads, you often don't even need to drill first.
     
  3. Sonic Reducer

    Sonic Reducer Monkey

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    sounds like a tough one since the bolt head is recessed. its got lock tite on it probably eh?
    to start, alternate mild heat with strong solvent and tap the area lightly to work the solvent into the threads as best you can. basically you want to use the heat for a bit of expansion and shock the area with the cold solvent spray so there is movement inside the threads which helps to break the connection. you'll want to repeat this process until you get bored, then do it again. i've used that technique to free up a lot of rusty ass bolts. we have this stuff here called PB blaster and if you let it soak on some threads for a few hours with frequent respraying it works wonders... sometimes.

    first thing I would try for breaking it loose would be to clean the crap out of the allen head, its got to be carb cleaner, alcohol or acetone, something without a residue and epoxy an allen wrench in the bolt to try and get some bite. make sure everything is really clean, and you got the epoxy in there tight, and the epoxy is fully cured. the bolt is done anyway and the allen wrench can be cleaned off.

    another thing you could try if you cant get the epoxy to bite is using a dremel(just buy a cheapie theyre the dogs bollox) with a very small worn down cutoff wheel to cut your slot in the bolt head, then take an impact driver(hammer driven) with a very small sharp flathead and patiently hammer the notch deeper until you have enough meat to take a swing at it. a sharp chisel of the correct width wouldnt hurt. the impact driver is kind of an old school tool that is absolutely essential for working on stuff with screw driver heads. the shock it transmits to the bolt works wonders for helping to break the connection in the threads while keeping the head in good condition because lots of force is going straight into the bolt at the same time as it is twisting.

    if the other options dont work then this probably won't, but get a set of left hand drill bits. those work pretty well when the bolt is not very frozen.

    good luck. :bonk:
     
    #3 -   Feb 17, 2009
    Last edited: Feb 17, 2009
  4. MisterMental

    MisterMental Monkey

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    stud extractors or try getting like a 1/4" ball putting it in the head of the rounded bolt and braying it with hammer, this can sometimes work, if not stud extractor, failing that get it spark eroded.
     
  5. Jm_

    Jm_ Turbo Monkey

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    If there's locktite, step one is to put a soldering iron on the bolt for a while to loosen the locktite.

    I've used the expand/contract the interface before in other applications, but usually when I'm taking out a bolt on a bike it's been locktited in there, so you have to loosen the loctite with heat.

    Step two is to drill out the bolt with a much smaller bit, so you have something to grab with the easy-out.

    Put the easy-out on your drill, don't use a super-fast setting, put it in the hole, select the correct direction, and extract the bolt. The easy-out is a reverse threaded bit that "grabs" the bolt and pulls it out. I've had good success with it multiple times.

    Back in the day I did drill out the middle of some stuck bolts which seemed to releave some pressure and they then came out fairly easily, but I wouldn't waste time with that, go to the hardware store and get the appropriate size easy-out. They come in real handy. I don't know if there is some reason why you can't use the easy-out extractor, but it's worked well for me.
     
    #5 -   Feb 17, 2009
    Last edited: Feb 17, 2009
  6. MisterMental

    MisterMental Monkey

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    easy-outs are called stud extracters in the uk, i asked for easy-outs and got looked at funny.
     
  7. Spunger

    Spunger Git yer dumb questions here

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    Just remember, if you break off an easy out (or stud extractor) off in the bolt, GOOD F'n luck getting that out. They are made of hardened steel. It'll take some time to drill out.

    I did this on my motorcycle a month ago. What should have taken an hour took forever. I probably had the wrong bits and drill but I had to do with what I had. I did use Cobalt drill bits which seem to do well on metal, but again after drilling and drilling I'm sure it went dull.

    Good luck!
     
  8. Jm_

    Jm_ Turbo Monkey

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    Ok, but would you need a pair of them or just one? :banana:
     
  9. MisterMental

    MisterMental Monkey

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    uh 1 if it fits the rounded head right
     
  10. spinner

    spinner Monkey

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    Want to save yourself the time and effort trying the methods above with no guarantee of success ? Take it to an engineering shop with TIG capabilities. They can apply some weld metal on the bolt head , then weld a nut to it for easy removal after everything has naturally cooled.

    The best thing about this method is the heat that goes into the bolt (and subsequent cooling) helps the bolt lose its grip on the thread and they generally come out very easily. I do this regularly where I work on anything from M3 to 1" studs. My success rate is 99.5% ( In 20 years I've had 2 studs that wouldn't budge) We get quite a few come in with broken Easy Outs stuck in there.

    The only downside is you may lose a little paint from the radiant heat , very minimal though. I hope that all makes sense , otherwise I'll do a quick sketch in Paint to help explain.
     
  11. ChrisKring

    ChrisKring Turbo Monkey

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    You can try a left handed drill bit too. This is different that an easy-out.
     
  12. - seb

    - seb Turbo Monkey

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    Cheers for all of the feedback guys! I have nothing at home that I can do this with, so I think I'll just take it to an engineering shop that can probably do it for me.
     
  13. Sonic Reducer

    Sonic Reducer Monkey

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    for what you will pay a shop to pull that bolt out, you could probably buy the tools necessary plus some beer.


    next time put some anti sieze on the bolt and don't overtighten. it's a 3mm bolt for a reason, doesnt need a bazillion Nm.
     
    #13 -   Feb 18, 2009
    Last edited: Feb 18, 2009
  14. ohio

    ohio The Fresno Kid

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    As someone who has done what Spunger did more than a few times, I highly recommend using extraction bits/EZ outs by hand with a T-wrench.
     
  15. ChrisKring

    ChrisKring Turbo Monkey

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    Yes, even then you need to be careful. I snapped a carbide EZ-out off in an aluminum head trying to remove a exhaust manifold stud. Not fun. I build a drill fixture to run an end mill into the head rather than removing the head.
     
  16. kamomatt

    kamomatt Chimp

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    I have the DHi also 2 now, know which bolt you speak of.
    Don't use heat you'll melt the two plastic bushings, hard to find and expensive if you do.
    Center punch the bottom of the bolt and drill it out backward you might get lucky and catch the screw and drive it out with the drill. TAKE YOUR TIME!!!!
    I'm always looking for old DHi stuff cheap. I saw a cracked frame on pinkbike 1-2 years ago Canada I think.
    Recently I saw items on ebay crazy cheap for I-drive month or two ago. Brand new NOS stuff, Indiana USA the eccentric which you may need. Search ebay I've had luck just with google also.
    I have some spare stuff, some that I won't part with some I will.
    KEEP EM FLYING BROTHER