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Old 04-13-06, 01:08 PM   #1
Magictofu
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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?
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Old 04-13-06, 03:24 PM   #2
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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
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Old 04-13-06, 07:41 PM   #3
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JB Weld.
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Old 04-13-06, 08:05 PM   #4
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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.
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Old 04-13-06, 08:06 PM   #5
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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
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Old 04-13-06, 08:08 PM   #6
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Helicoil-that's the word I was looking for. Thanks halfspeed! (completely forgot about tapping too..)
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Old 04-13-06, 08:15 PM   #7
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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.
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Old 04-13-06, 09:26 PM   #8
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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?
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Old 04-13-06, 09:58 PM   #9
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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.
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