How to undo a hex bolt with round head?

Discussion in 'Bicycle Mechanics and Repairs' started by Spoked Wheels, 12 Apr 2008.

  1. Spoked Wheels

    Spoked Wheels Guru

    I asked my LBS sometime ago to adjust the disc brakes for me and they were fine after that but I did not realise until the other day that he damaged the head of the bolt and now I cannot remove the bolt. The shape of the bold does not allow for pliers either...

    Any ideas how to solve this problem?

    Thanks in advance

  2. Smokin Joe

    Smokin Joe Legendary Member

    Drill a hole in the head and tap a slightly oversize Torx bit in, that should provide enough leverage to undo it.
  3. yello

    yello Legendary Member

    That's not very clever of them. I'd not go back there again...

    I managed to remove a similarly knackered hex bolt by driving a slightly larger torx bit (the starry shaped one) in and undoing that. It knackered the torx bit (not that I've ever found any other use for them anyway!) but it got the bolt out.

    Edit: I see SJ does the same!
  4. OP
    Spoked Wheels

    Spoked Wheels Guru

    No, it's not very clever - I think he did it on purpose - I don't think he likes people doing repairs themselve :smile: - I asked him to install pedals for me and he tight them so hard that next time I need to replace the pedals I will have to take the bike to the shop. I'm not using that LBS anymore.
  5. barq

    barq Senior Member

    Birmingham, UK
    To be honest I'd go back to the LBS. If they are so fundamentalist about doing the wrenching on people's bikes then let them fix this one.

    Otherwise... Is this one of the rotor bolts or on the caliper? I guess my normal mode of attack after the torx key method would be a very strong adhesive (araldite?) on a sacrificial hex/allen key and get a pipe or something for extra leverage. Another approach depending on where the bolt is located would be to cut a slot into it with a hacksaw and undo with a flate blade screwdriver (not so good for tight bolts). Or cut two sides of the head off and get some molegrips on. After that you are getting into more destructive areas like drilling the bolt out or using a reverse drill bit.

    Good luck, a stuck bolt is a pain when it happens but you can almost always sort it out.
  6. simonali

    simonali Guru

    Are we talking about a hex bolt or a socket bolt? A socket bolt can sometimes be undone by using an imperial hex key which is slightly larger than the metric one and knocking it in e.g. a 7/32" is 5.55mm.
  7. OP
    Spoked Wheels

    Spoked Wheels Guru

    Thanks for the ideas....

    The bolt is on the caliper.

    It's a hex bolt.

    I thought about letting him fix the problem but I would end up paying him for the extra time anyway, I'd rather pay somebody else really.
  8. simonali

    simonali Guru

  9. 02GF74

    02GF74 Über Member

    used on Fords and volvos, probably other cars too.
  10. Dave5N

    Dave5N Über Member

    Drill and use a screw remover
  11. robbarker

    robbarker Well-Known Member

    Rounding is normally caused by insufficient insertion of the hex wrench - there may be some undamaged socket at the back end. If you tap your hex wrench in with a rubber mallet you might get enough purchase.
  12. Sounds like a ham-fisted and cack-handed mechanic using worn-out tools and cheap bolts.

    If tapping an alen-key or torx driver into the wound fails just drill out the bolt, attacking it with a hacksaw or mole grips risks scratching the frame or caliper.

    Always drill steel slowly using lots of pressure.
  13. simonali

    simonali Guru

    Seems to be some confusion here. I asked whether it was a hexagonal bolt or a socket cap and the answer came back as the former, so knocking an Allen key into it will be impossible!

    A rounded off hex bolt can be drilled out and/or removed with a screw extractor, but you have to drill dead centre, not slip and have all the tools to do the job. Nearly everyone has a set of grips or pliers, though.

    Maybe we should make people post pictures in these type of threads? A thousand words an' all that!
  14. Alcdrew

    Alcdrew Senior Member

    If it's a hex headed bolt, that is now round. Then surley the easiest option would be either mole grips or better pipe wrench.
  15. Fiona N

    Fiona N Well-Known Member

    It might not be personal:sad: I usually find bike shops do up any given bolt or fixing far tighter than the maker's specs suggest. I reckon it's to make sure nothing comes undone and creates a liability for them - sad but there you go.

    Or it could just be insecure males showing off how strong they are ;)
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