Advertise on Bikeforums.net



User Tag List

Results 1 to 9 of 9

Thread: Broken thread

  1. #1
    Senior Member
    Join Date
    Apr 2005
    Posts
    309
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Broken thread

    I just realized that the thread on one of the braze on on my fork is broken and that the screw which lock my front rack in place is getting loose ... Is there something that can be done to fix the problem?

  2. #2
    Senior Member kamoke's Avatar
    Join Date
    Jan 2006
    Location
    st.johns, NL
    My Bikes
    Trek 1000c, Trek 520.
    Posts
    111
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    If the braze-on goes right through the tube then you could try a screw that goes through to the other side and get a locknut for the other end. This is a scamp solution but it would work.
    No suggestions if it doesn't go through all the way though - sorry

  3. #3
    Senior Member Old Hammer Boy's Avatar
    Join Date
    Aug 2005
    Location
    Utah
    My Bikes
    Trek, Cannondale Tandem, Surly LHT
    Posts
    1,082
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    JB Weld.

  4. #4
    Caffeinated. Camel's Avatar
    Join Date
    Aug 2004
    Location
    Waltham, MA
    My Bikes
    Waterford 1900, Quintana Roo Borrego, Trek 8700zx, Bianchi Pista Concept
    Posts
    1,541
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    If you can get the nut out, there are save a thread inserts which you might be able to buy (not sure if they make them with that small a diameter). They reduce the inside diameter, so you would have to use a small nut. Better than a quickie fix, at least untill you can have a new one brazed on.

    I don't believe Riv-Nuts (?most bottle cage bosses) would work in a rack application, but worth asking your good local bike shop.

    Lastly go with zip ties & wire.

    I wouldn't go with JB weld unless it's just for around town. You would most likely have to drill to get your rack off.
    mmmm coffeee!

    email: jfoneg (_"a t symbol thing"_) yahoo (_"period or dot"_) com

  5. #5
    Senior Member halfspeed's Avatar
    Join Date
    Nov 2003
    Location
    SE Minnesota
    My Bikes
    are better than yours.
    Posts
    10,737
    Mentioned
    32 Post(s)
    Tagged
    0 Thread(s)
    1) retap the threads with a tap if that doesn't work...
    2) Insert a helicoil if there is enough material in the braze-on to handle the larger hole

  6. #6
    Caffeinated. Camel's Avatar
    Join Date
    Aug 2004
    Location
    Waltham, MA
    My Bikes
    Waterford 1900, Quintana Roo Borrego, Trek 8700zx, Bianchi Pista Concept
    Posts
    1,541
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Helicoil-that's the word I was looking for. Thanks halfspeed! (completely forgot about tapping too..)
    mmmm coffeee!

    email: jfoneg (_"a t symbol thing"_) yahoo (_"period or dot"_) com

  7. #7
    NoPo nateted4's Avatar
    Join Date
    Jan 2006
    Location
    Portland, OR
    Posts
    47
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Old Hammer Boy
    JB Weld.
    NO NO NO NO NO.

    JB weld has failed me for the last time. I've never gotten epoxy to do anything but fail on me at inopportune times. It makes me bitter.
    Saddle Stitching is like Razorblades for Your Crotch.

  8. #8
    Senior Member
    Join Date
    Apr 2005
    Posts
    309
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Ok... I'll add more details here... there is still 'some' thread and the bolt is still in. I can't screw it very tight without destroying what's left. Right now, the rack is held in place with a zip tie but I'm sure it won't last very long. Since there is still some thread left, do you think there is an easy way to fix my problem... epoxy does not seems very popular but that was the first thing I had in mind... but I thought it would make removing the rack almost impossible.

    After googling helicoil, I found a few options but they all seems quite complex, especially for someone like me who has 0 knowledge in this and no tools. How solid would it be compared with normal braze on? What kind of business could be able to do that kind of job? What should I look for in the yellow pages?

  9. #9
    Senior Member halfspeed's Avatar
    Join Date
    Nov 2003
    Location
    SE Minnesota
    My Bikes
    are better than yours.
    Posts
    10,737
    Mentioned
    32 Post(s)
    Tagged
    0 Thread(s)
    In a previous life I fixed light industrial machinery for a living. (Now I fix buggy software.) Helicoils are really not that hard to do. You get a kit for the size bolt you need to fit. It comes with coils, a drill bit, a coil inserter and a tap. You drill the current hole with the bit, then tap it with the tap. Next, you wind the coil on the insertion tool and slowly turn it into the hole. The coil stays in as you then wind the insertion tool back out. The inside of the coil serves as a perfect set of new threads. Oh yeah, use plenty of oil in the process.

    Still, before doing a helicoil I'd try to retap it with a tap. Tap and die kits can be had at home improvement stores but metric sizes are harder to find and you may be better off looking for an industrial supplier. Even individual taps can be had. A tap is basically a cutting tool that cleans up the threads of an existing threaded hole or creates new ones by simply screwing it in. A tap designed for the size hole you need to fix needn't be expensive.

    If you don't have enough material to support the coil and maintain the strength of the braze-on, you may need to go down a size in the rack mount bolt. Of course, that might not be as strong.

    If all this looks scary to you, see if you can find a local machine shop that can help you. You're looking for a guy who can do one-offs and prototypes, not a big CNC production operation. Maybe even an auto repair place will help you find someone since they usually know someone who can turn brake rotors. Maybe even a guy who customizes motorcycles can do it.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •