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  1. #1
    mtbr member
    Join Date
    Feb 2004

    Small hex bolt problem

    I'm replacing a bent derailuer hanger. The hanger is held in place by two 2.5mm hex bolts. First one came out just fine. Second one is stuck in there real good and in the process of trying to get it out I have managed to round off the corners of the bolt. Any advice on A) getting the bolt out and B) avoiding this problem in the future?

  2. #2
    Fat-tired Roadie
    Reputation: AndrwSwitch's Avatar
    Join Date
    Nov 2007
    Ooh, tough.

    Two major points. Penetrating oil around the bolt. Since you have access to both sides, try both sides.

    Do you mean hex as in you use a box wrench to get it off? Or as in you use an Allen key. Is 2.5 mm the size of the Allen key or the nominal size of the screw?

    If it's a screw that you turn with an Allen key, a left-handed drill bit is a good way to get them out. Bolt extractors are great too, but may not be available small enough.

    Since the screw is very small, a full-sized drill may be hard to use precisely enough. A milling tool could be easier to work with.
    "Don't buy upgrades; ride up grades." -Eddy Merckx

  3. #3
    mtbr member
    Join Date
    Apr 2010
    You can also try a torx bit. One might fit in the rounded off area and bite enough to get it out. You can also use easy outs. They make them for removing SHCS that are rounded like you have, but I am not sure if they are that small.

    Good luck,

  4. #4
    mtbr member
    Join Date
    May 2007
    ^^Both of these. I once stripped out the Allen head on one of the bolts that held my rear brake master cylinder to the handlebar. I tapped in a torx bit and it came out no sweat. If that doesn't work, use an easy out. You just drill the right size hole, and push and turn the left handed screw, and out it comes. Very easy, and it works.

    Sent from my SCH-I545 using Tapatalk

  5. #5
    mtbr member
    Reputation: sasquatch rides a SS's Avatar
    Join Date
    Dec 2010
    Grind a small flat notch in it with a dremel and use a small flathead to remove it. I've done this on many small bolts for all sorts of applications (bikes and not bikes) with great success. To me, this seems the easiest approach, and you can re-use the bolts as flat heads also, to avoid the issues small hex bolts can have. If you have a dremel, this is what I'd suggest. If not, all other options mentioned will achieve the same results.

  6. #6
    Trail Tire TV on blogger
    Reputation: thomllama's Avatar
    Join Date
    Oct 2007
    all the above advice is good.. avoid it next time by taking a bit of plumbers tape (teflon tape) and do a wrap or 2 before assay.. no more than 2 wraps as it'll just add thickness at that point and end up binding. This way the threads won't stick and the tape actually helps hold it while making it easy to take apart later.. win win.

    do it with anything threaded on a bike except the brake rotors which have a possibility of getting too hot and melting the tape. It works better than any of the loctitie's and doesn't leave the crust behind they do when you do repairs.
    Going to try and bring Trail Tire TV back. go take a look...

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