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Bolt Sheared Off - Help

SlipknotjonnySlipknotjonny Posts: 197
edited March 2009 in Tour & expedition
I was fitting my pannier rack to my frame today, something which I do regularly as I do n't want the rack on the bike all the time.

As I was tightening one of the Allen bolt into the boss on the seat stay it sheared off, I have now had to cobble something together out of cable ties, which whilst just about doing the job does look a bit Pony to say the least.

Will a bike shop be able to drill out the remainder of the bolt and re-tap the mounting boss or am I, as we say around hear, up 5h1t creek?


  • paul27paul27 Posts: 515
    Bad luck chap,you dont know your own strength :) the LBS should be able to sort it out for you.

    Good Luck
  • crankycrankcrankycrank Posts: 1,830
    Have you tried using some kind of pointy object to turn the bolt out? Could be just loose in the hole and easy to coax out.
  • dilemnadilemna Posts: 2,277
    I've no idea what bike maintenance you do, the tools you have or your general capabilities, but if it were me I would try drilling out the sheared piece myself.

    First you need a metal drill bit ie one for drilling metal preferably one that is slightly smaller than the actual bolt that screws into the hole. And a drill……You can use the remains of the bolt head or the corresponding side to compare against the drill bit to make sure you do not drill out too much making the hole too large which is fatal. If you do you will need a larger bolt. Ignore the threads of the bolt and compare diameter across the bolt inside the threads with the drill bit which should not be larger than this diameter otherwise you will drill out metal you want to remain in the hole to cut your thread into.

    Get a cutting bit that is the size of your bolt eg M6 or M8 bolt. You can get dye and cutting sets from Machine Mart or a decent hardware DIY shop for about £10. Before cutting new threads using the cutter try to see if you can unblock the existing threads which will still have residue of the bolt you have just drilled out in them. This might not be possible so go straight to winding in the cutting bit which will free the threads as you slowly turn it in. But before you do spray some WD40 or GT85 into the hole as it can act as a lubricant/cutting agent. Slowly and gently twist in the cutting bit turning it gently back and forth gradually going a little bit further in each time. Keep it square to the hole and tube. I shouldn't imagine the threads are too deep so should be in pretty quickly. Once drill cutting bit moves freely turn it fully in and out of the hole several times lubricating as required. Clean up any residual metal shards or swarf.

    Re-fix rack and insert new bolt with some grease either LM or Copper grease on the threads to stop it seizing. Only tighten the new bolt until it will screw in no more with fingers or gently using a spanner or Allen key and then a further tweak of a 1/4 of a turn max. Use a spring washer to stop it coming loose. Check bolt(s) after a ride or few weeks to make sure they have not come loose

    Hope this helps otherwise deposit bike at your local LBS.
    Life is like a roll of toilet paper; long and useful, but always ends at the wrong moment. Anon.
    Think how stupid the average person is.......
    half of them are even more stupid than you first thought.
  • VividVivid Posts: 267
    If the head has come off then you may be able to remove it using your fingers.
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