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Rounded allen bolt

weaponsweapons Posts: 367
edited November 2009 in Workshop
I tightened the allen bolt on the stem cap, but have managed to round off the edges, so now can't loosen it with an allen key.

Do any forum users know how I might be able to get the stem cap off now, as I need to tighten the headset?



  • laelae Posts: 555
    Eeeeesh. The problem is that it's flush with the cap and very small!

    It's too small to weld a nut to, but as cap bolts aren't done up very tight, gluing an allen key in might work. Or getting a torx bit (the 6-pointed star ones) that's a bit bigger than the hole, and hammering it into the soft aluminium.

    If that doesn't work... you could very carefully use a drill to remove the cap (drill a circle of little holes to remove the bulk and use a pair of pliers to twist off the rest) and then you'll have the sides of the allen bolt exposed - then you can use a pair of pliers to turn it. Probably a bit dangerous though.
  • term1teterm1te Posts: 1,462
    How about drilling two small holes either side of the bolt head so that you can get some purchase with a flat head screwdriver? If it was sitting proud you could cut a slot with a hack saw to get at screw driver in.
  • nicklousenicklouse Posts: 50,675 Lives Here
    just drill the top off the bolt and replace it.

    if you rounded out the top cap bolt then your headset is too tight or you forgot to undo the stem bolts first.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Like said you should try and drill it out. Not much to damage in there, just the cap the bolt and possibly the starfangled nut, all of which can be replaced easily.

    Seriously though that is a pre-tensioner for the headset and should not be used to tighten the headset unless the stem bolts are open, it adds nothing to the stiffness of anything once the stem is tightened.
  • crakercraker Posts: 1,739
    ... or try to cut a slot into the nut with a chisel (hard work) or very small grinder - think you'll end up destoying the cap though. I imagine they're interchangeable though I've no idea where to get one without the rest of the headset.
  • Glue the allen key in place with epoxy resin.
  • weaponsweapons Posts: 367
    Many thanks all for the responses. It looks like glue and if that doesn't work drilling the bolt might do the trick.

    Chunkers, I think that's just it - not loosening stem bolts first. I am a clutz mechanically but am learning (albeit through error!)... :)
  • Smokin JoeSmokin Joe Posts: 2,706
    A slightly oversize torx bit will give enough grip on a rounded Allen head to undo it.
  • rakerake Posts: 3,204
    edited March 2010
  • geoff_ssgeoff_ss Posts: 1,201
    BobGeldart wrote:
    Glue the allen key in place with epoxy resin.

    JB Weld is good stuff for that. I get mine from the local car spares shop. It takes a good 12 hours to go off, though. It's fairly expensive, too but it keeps so it's on hand for other jobs you may need.

    As a general rule slower epoxies tend to be stronger. 5 minute ones are not very strong and I only use them occasionally.

    Old cyclists never die; they just fit smaller chainrings ... and pedal faster
  • Use a screw extractor, they are like thread taps but reverse threaded. ... ctor%20Set
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