Crank Arm Pinch Bolt

thefartingcockeral
thefartingcockeral Posts: 394
edited July 2018 in MTB workshop & tech
Hi all, i need some advice. I have gone to remove my XT crank arm and the crank arm pinch bolt top has had the hex part rounded out buy the LBS who serviced it last year. Is there anything I can do to salvage this or do I take it to another LBS to sort out?

Comments

  • cooldad
    cooldad Posts: 32,599
    You can try hammering a torx bit in.
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  • thefartingcockeral
    thefartingcockeral Posts: 394
    Hi Cooldad,
    Thanks for that. I will trill it later.
  • steve_sordy
    steve_sordy Posts: 2,453
    Take it back to the LBS that you believe damaged it and just ask them to remove it. Be all innocent. :wink:

    If they ask any questions, just say it hasn't been touched since the last time it was with them. You don't have any tools do you?
  • steve_sordy
    steve_sordy Posts: 2,453
    Proper suggestion now:

    Obtain two new bolts, do it now.

    There are two pinch bolts, and they work together. So if you have removed one, put it back nice and tight. Check that it too is not about to round out! (Or use one of your shiny new ones).

    The second bolt will have relieved the pressure on the damaged one, making it easier to remove. Try an oversized Torx key as suggested. You might have to hammer it in to get a good grip.

    If all else fails, drill it out, but from the bottom (other end of the bolt to where the Allen head is). Because you are drilling from the bottom, there is a very good chance that the Allen screw will come out naturally during drilling. But start with a centre punch and a small drill to create a pilot hole for a drill of the correct size. That way, you will avoid damaging the crank if the point of the drill wanders at start up.
    As soon as the damaged bolt starts to move, stop drilling and slacken the second bolt, or that may get jammed in too.

    Once all is well, use two new bolts!
  • 02gf74
    02gf74 Posts: 1,171
    Unless the piece is held firmly, trying to drill the bolt out, especially from the bottom (the hex recess would act as a guide) is likely result in a broken drill bit. If this happens, it become more difficult as the drill is hardened steel.

    You could use a saw or dremel in the gap to cut the bolt so that the crank can be removed, clamp it in a vice and use drill press to drill out the bolt.
  • thefartingcockeral
    thefartingcockeral Posts: 394
    The bike shop that did the work has closed recently so cannot take it back their. I tried knocking an oversized torx head into it but did not work.
  • milemuncher1
    milemuncher1 Posts: 1,472
    Smack a slightly bigger than necessary torx bolt in, then extract the rounded bolt, and replace it. Make a note of never going to the place that messed the job up, ever again.

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