Drilling holes in a steel bike frame

Discussion in 'General Cycling Discussions' started by Accy cyclist, 15 Apr 2018.

  1. A friend of mine has bought a bottle cage,only to find there aren't any holes to screw the cage to the frame. She says she's going to ask someone to drill two holes into the downtube. I told her that it might affect the strength of the frame. Am i right? I'm almost certain the frame is steel,though it could be aluminium. The bike's about 30 years old.
     
  2. Drago

    Drago Guru

    Location:
    Central Trumpland
    I wouldn't recommend it. Why not just use clips, or get a handlebar mounted model?

    And when she's drilled the holes, then what? Does she have a rivnut tool, or is she capable of welding in bosses?
     
  3. winjim

    winjim A youth of interminable age

    She'd then need to install those threaded doodads to actually mount the cage to. I'm sure a proper frame builder could do it but it seems a lot of hassle. Just get a band on.
     
    Illaveago, Accy cyclist and Drago like this.
  4. OP
    OP
    Accy cyclist

    Accy cyclist Guru

    I will put all suggestions to her.:okay: I told her it seems a bit extreme,just so you can have a water bottle. I did suggest using tape or tie backs,but she likes the idea of holes in the frame,for some reason.:rolleyes:
     
    winjim likes this.
  5. Reiver

    Reiver Legendary Member

    a couple of 5 mm holes wont affect the strength of the frame, but what then ? if you tap them to take an M5, I doub't the thickness of the frame would provide enough strength to with stand someone pushing and pulling a bottle in and out of the holder. You need to get a proper boss welded onto the frame (then it will all need repainting) whole things a bad idea.
     
    raleighnut and Accy cyclist like this.
  6. biggs682

    biggs682 Smile a mile bike provider

    Location:
    Northamptonshire
    Get a band on style no holes to drill


    IMG_20180415_112307951.jpg
     
    Last edited: 15 Apr 2018
  7. si_c

    si_c Veteran

    Location:
    Wirral
    If you drill holes in the frame, that's what you end up with, holes in the frame. A steel bike will have tubes no more than a couple of mm thick. You'd need to then have the bolts fitted as mentioned above, which won't be cheap.

    There are plenty of options, I got one from elite for my 70s Peugeot, which has no bosses, cost less than a tenner from Halfords.
     
    Accy cyclist likes this.
  8. Smokin Joe

    Smokin Joe Legendary Member

    You need to paint that back door instead of messing about with bikes.
     
    bigjim, raleighnut and biggs682 like this.
  9. mcshroom

    mcshroom Bionic Subsonic

    Location:
    Egremont, Cumbria
    I wouldn't drill into the frame, and anyway you'd still need to install some rivnuts. The job starts to become a bit expensive for just fitting a bottle cage then. Instead I would use these: -
    https://www.ebay.co.uk/i/192467353607

    They are the same as @biggs682 has on that frame and held a second bottle on the set tube of my audax bike fine for a while.

    I've also used the Elite ones from Halfords, which work just as well IME, and have screw in mounting holes rather than tying the cage to the frame so will take the fashion carbon/plastic cages that don't have those bits of plate to clamp. They don't look as nice though IMHO.

    If they use clamped mounts, make sure they put some tape under them to prevent paint damage.
     
    Last edited: 15 Apr 2018
    HLaB and Accy cyclist like this.
  10. +1 for using band-on cages.
     
  11. Alan O

    Alan O Über Member

    Location:
    Liverpool
    Absolutely yes, tell her to stop drilling now. The thickness of the tube is simply not enough to screw in to (steel tubes are very thin, and aluminium is soft), and she'd need proper mountings fitted - with either metal, you don't just drill and screw into it.

    As others have said, you can get strap-on bottle mounts - I used them for years on an old bike.
     
    Accy cyclist likes this.
  12. KneesUp

    KneesUp Veteran

    Drilling holes in the frame won't unduly change it's strength if you then fill the hole with something (a rivnut or nutsert - which you will need so there is a thread) If it did, we'd here more about bikes failing where the bottle cage or pannier mounts are.

    You can get M5 inserts quite cheaply - about 10p each of you buy 50 off eBay. You friend will need a rivet tool that can take rivnuts.

    EDIT - drilling into a narrow cylinder may be quite tricky - if your friend slips with the drill it might get messy. An LBS worthy of the name will be able to do it I'm sure.
     
    Accy cyclist likes this.
  13. Dave7

    Dave7 Veteran

    Location:
    Cheshire
    Maybe she wants holes drilled to make it lighter so it will go faster.
    On the other hand :rolleyes:
     
    classic33 likes this.
  14. OP
    OP
    Accy cyclist

    Accy cyclist Guru

     
  15. OP
    OP
    Accy cyclist

    Accy cyclist Guru

    I'll tell her that one. I don't know if she'll like it though.:laugh:
     
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