Removing sheared bolt ends

Mendip rouleur
Mendip rouleur Posts: 163
edited June 2016 in Workshop
Anyone got any successful experience of extracting a sheared 4mm Allen bolt end from a carbon recess? I have a Trek Madone 209 vintage, with a carbon seat post cap, one of the bolts sheared yesterday and unless I can get the bolt end out I'm going to have to replace the whole cap, at a very painful price.
“I ride my bicycle to ride my bicycle.”

http://mendiprouleur.blogspot.com/

Comments

  • sungod
    sungod Posts: 17,340
    what the easiest way would be depends on exact situation, was it seized or free to turn and simply over tightened, blind hole or both ends exposed, etc. etc.

    assuming you can't just use a pick to slowly rotate it out, or slot it to use a screwdriver, you could use a dremel to drill a hole in the exposed end then use a screw extractor to remove it, as long as the bolt is steel that should be straightforward, if it's a ti bolt it'll be tougher but you can still do it
    my bike - faster than god's and twice as shiny
  • keef66
    keef66 Posts: 13,123
    Wot he said on all counts. If it's not a blind hole and you can get to the other end of the bolt you may be easier / safer to drill a central hole there and use an extractor. Some times using this approach the very act of drilling it is enough to unscrew it back out the way it came in.
  • keef66
    keef66 Posts: 13,123
    Just googled for images of said thing and it looks like a single bolt going into a blind hole :(
  • Mendip rouleur
    Mendip rouleur Posts: 163
    Sadly it is a single bolt into a blind hole.
    “I ride my bicycle to ride my bicycle.”

    http://mendiprouleur.blogspot.com/
  • sungod
    sungod Posts: 17,340
    drill + extractor (and a tap wrench to turn the extractor)

    the fiddly bit is drilling the hole, to avoid the bit skidding it's best to start out with a sleeve around the drill bit to keep it centered in the hole, start slow, once the bit has gone in 1-2mm you can remove the sleeve and speed up

    avoid cheap extractor bits, if they're poorly made they may just snap, irwin are ok i think, this set includes the matching drill bits (for 4mm the #1 extractor should be ok), if you have a good tool store nearby they may sell them individually

    https://www.amazon.co.uk/Irwin-Industri ... B0025PKJYA

    if you're not sure about diy, any decent lbs will be able to do it
    my bike - faster than god's and twice as shiny
  • keef66
    keef66 Posts: 13,123
    I have a set of Irwin sockets for gripping rounded bolt heads. Seem pretty robust. Used with an improvised 4 foot breaker bar to remove a stubborn bolt on son's aging Fiesta

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