Removing allen bolts

Discussion in 'Bicycle Mechanics and Repairs' started by Yellow Fang, 1 May 2010.

  1. Yellow Fang

    Yellow Fang Guru

    I'm trying to get a couple of allen bolts out of the seat tube of my bike so that I can fit a rack.They don't want to come out though. The allen key sockets are rounded off, and they seem pretty well corroded on. I've tried dripping oil where the sides meet. I've also taken a hack saw to one of them and cut a groove across so I could use a flat-blade screw driver on it, but still no joy. Any ideas anyone?
  2. buddha

    buddha Veteran

    Mole grips? Try tightening (a little first) and then unscrewing.
    Although I had a similar problem and ended up drilling them out - which ruined the threads. Ended up using a single long bolt (and nut) that goes through both holes.
  3. PpPete

    PpPete Guru

    Chandler's Ford
    Get a Torx bit that's a little too big for the socket. Hammer it in.
  4. Davidc

    Davidc Guru

    Somerset UK
    There are devces called "reverse threaded tapered taps" for that type of job.

    They are hardened steel, the same stuff normal taps are made from. When put in the hole and turned anticlockwise in what is the usual unscrewing direction they cut in and tighten, then allowing you to get the siezed bolt out.

    If the offending bolt is too well in it is possible to break them, but usually they work. The real pig is getting the tap out of the bolt afterwards though. You need a good vice.
  5. Svendo

    Svendo Veteran

    I managed to remove some corroded-in bottle cage allen bolts with protruding heads by first cutting the bottlecage away, then filing two sides of the bolt heads flat so I could get a good grip with an adjustable spanner. Following overnight treatment with lots of WD40 I was able to break the corrosion with gentle hammer traps on the spanner. Phew! Frame saved.
    I think I had a lot more leverage than using a screw driver in a slot that you've tried.
    Bolts all get a good greasing or copperslipping and occasional loosening retightening now.
  6. GrasB

    GrasB Veteran

    Nr Cambridge
    Yellow fang, are you trying to take the saddle off or is this a seat post clamp? If it's a seat post clam personally would be tempted to cut the clamp & discard then buy a new on (assembling with some assembly grease or copper slip)
  7. snorri

    snorri Legendary Member

    Clearly a sympton of aging, you will fix the allen screw and what will fail next?
    Get yourself a new bike, it's the only long term solution.;) :biggrin:
  8. Smokin Joe

    Smokin Joe Legendary Member


    Never known it to fail.
  9. Matthames

    Matthames Über Member

    East Sussex
    Invest in an impact driver. I have one and it is usually my first port of call when I have a stubborn bolt or screw. A few whacks with the hammer and impact driver tends to loosen most frozen bolts.
  10. GrasB

    GrasB Veteran

    Nr Cambridge
    Assuming that the bits actually locate properly in the holes. Once rounded impact drivers are fairly useless ime.
  11. Globalti

    Globalti Legendary Member

    Can you support the stays so that they are really solid? Set that up then give the bolts a sharp tap with a light hammer and a punch, straight down. This will break the bond around the threads.

    Don't hit them so hard that you crush the stays though!
  12. Zoiders

    Zoiders New Member

    Ice Station Zebra
    Once they get worn and rounded out do the following.

    Buy a cheapy set of imperial of allen keys and you will find one that is between the metric sizes and will fit in a worn metric allen head bolt very snugly, it's a cheap key so tap it in if needed.
  13. OP
    Yellow Fang

    Yellow Fang Guru

    Thanks for all the tips. I will check them out.
  14. OP
    Yellow Fang

    Yellow Fang Guru

    Both allen bolts are now extracted :biggrin: Used a combination of WD40, a Torx bit (so that's what they're for), a hammer and and adjustable spanner to remove one. The other was more tricky. I had to file down two sides of the bolt and use and an adjustable spanner. The rack is now on :tongue: but I suspect I'm going to have a similar problem getting it off, in time. Those allen key bolts round off so easily.
  15. Gerry Attrick

    Gerry Attrick Lincolnshire Mountain Rescue Consultant

    Just use plenty of copperslip or similar on the new bolts. They will then never seize.
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