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  1. #1
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    Stripped Anchor Bolt Hole. Rear C-record mech. PICS.

    EDIT: I've updated this thread with my results so scroll down if you're interested.

    I recently purchased a very nice first generation C-Record rear derailleur and while installing it noticed the cable anchor bolt hole is stripped. Here are a few photos for reference. First photo is with the M5 (5mm) bolt and cable plate installed, second photo is without the plate and bolt, third photo is just for location reference.

    So I know most of you will suggest I drill out the hole and re-tap to the next largest size (M6) and there is certainly enough material around the hole to do so. However the hex head of an M6 bolt is considerably larger, and would be an eyesore on this rare classic derailleur. Perhaps I could get a nice chrome one. I've already searched for an allen head screw and a machine screw that would be less offensive, but have had no luck. I also would have to enlarge the hole on the small steel cable plate, and that seems like it would be a pain.

    I'm wondering if anyone has had experience with a Heli-Coil thread repair kit for a hole this small. I found one kit online here: http://www.sjdiscounttools.com/hel5546-5.html
    The heli coil threads are a little long. Can they be trimmed to fit shallower holes? Also, I'm open to any suggestions or input anyone can offer. Should I forget the heli-coil and thread and re-tap? I've heard thread repair kits can be stronger than the original hole. Whadaya think?
    Last edited by rollsroyce; 12-11-06 at 06:35 PM.

  2. #2
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    Heli-Coils rock. They can be trimmed to fit a shallow hole. The link you posted has them for a great price.
    Last edited by ISeeDeadHuffies; 12-08-06 at 06:03 PM.

  3. #3
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    Keep looking for an M6x1.0 allen or slot head machine screw. Every hardware and home supply store around me has them but probably in longer length than you need. A hacksaw will fix the length problem. Bike Tools Etc. has allen head metric bolts in a variety of diameters and lengths but the shipping would cost way more than the bolt.

    Another possibility is to use an M5x.8 bolt and put a nut on the other end. There certainly seems to be room for one.

  4. #4
    D=RxT
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    A nut is not likely to clear the inner cage.

  5. #5
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    Thanks to the both of you. I've already tried placing a nut on the other end. I found some very thin nuts (jam nuts maybe?) and it sort of worked, but barely cleared the body on the other side. I tried adding a lockwasher and there wasnt enough room for the lockwasher and the thin nut. Those photos are deceiving. Theres barely room when the derailleur is just sitting, but when you cycle the derailleur like its shifting, the nut on the other side hits the cage.

    Edit: beat me to it!

  6. #6
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    You can Helicoil it, it'll hold just fine.
    i ride bikes.

  7. #7
    8speed DinoSORAs Ed Holland's Avatar
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    I'd recommend a helicoil. They were developed originally to provide durable threading in aluminium alloys. I've only had call to use one on one occasion, to repair a thread on my car, but I was very satisfied with the result.

    Ed
    Get a bicycle. You will certainly not regret it, if you live.

  8. #8
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    Whats the heli-coil process? I know you drill out the hole, and tap it with some special tap? and then just screw in the heli-coil? Is there any thread locker needed for the coil? Just curious. Thanks for the help everyone.

    Edit: Also, how should I trim it? Does it matter which side is trimmed?
    Last edited by rollsroyce; 12-08-06 at 06:25 PM.

  9. #9
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by rollsroyce
    Also, I'm open to any suggestions or input anyone can offer. Should I forget the heli-coil and thread and re-tap? I've heard thread repair kits can be stronger than the original hole. Whadaya think?
    To use Helicoils, you have to expand the hole even larger in order to accomodate the coils. I say try it in stages.

    1. drill out hole slightly, tap for M6x1 bolt, get allen-head bolt with CORRECT CABLE-CLAMP WASHER. Using a flat washer doesn't grab the cable very well and requires excessive tightening in order to hold the cable, thus the stripped hole.


    2. next up is some kind of insert for same M5x0.8 threading (but get the allen-head bolt & correct washer). Helicoils are at the bottom of the list of thread repair kits in terms of durability & strength. A one-piece insert like Time-Serts or EZ-loks works much better.

  10. #10
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    Thanks. Am I not using a "CORRECT CABLE-CLAMP WASHER?" I'm using the OEM cable clamp part that came with the derailleur. Its not exactly a washer, but it seems to be of good design.

    Quote Originally Posted by DannoXYZ
    To use Helicoils, you have to expand the hole even larger in order to accomodate the coils. I say try it in stages.

    1. drill out hole slightly, tap for M6x1 bolt, get allen-head bolt with CORRECT CABLE-CLAMP WASHER. Using a flat washer doesn't grab the cable very well and requires excessive tightening in order to hold the cable, thus the stripped hole.


    2. next up is some kind of insert. Helicoils are at the bottom of the list of thread repair kits in terms of durability & strength. A one-piece insert like Time-Serts or EZ-loks works much better.

  11. #11
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by rollsroyce
    Thanks. Am I not using a "CORRECT CABLE-CLAMP WASHER?" I'm using the OEM cable clamp part that came with the derailleur. Its not exactly a washer, but it seems to be of good design.
    Sorry didn't take a close look at it, appears to be a simple flat washer. If it has a groove for the cable, then it's the correct part.

    I've found that the 1-piece thread-inserts works much better.

    Time-Serts


    EZ-lok
    Last edited by DannoXYZ; 12-08-06 at 06:40 PM.

  12. #12
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    Drill it for the next larger size, an M6 and use a button head style metric socket head screw. A stainless M6 @ 8mm long is a standard item in button heads. You just need to find a decent local fastener supplier.

    You may need to cut the length of the screw even shorter, so have a nut already on the screw to chase the threads. A nice washer under the button head ought to not show too much.
    Attached Images Attached Images

  13. #13
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    Quote Originally Posted by DannoXYZ
    To use Helicoils, you have to expand the hole even larger in order to accomodate the coils. I say try it in stages.

    1. drill out hole slightly, tap for M6x1 bolt, get allen-head bolt with CORRECT CABLE-CLAMP WASHER. Using a flat washer doesn't grab the cable very well and requires excessive tightening in order to hold the cable, thus the stripped hole.


    2. next up is some kind of insert for same M5x0.8 threading (but get the allen-head bolt & correct washer). Helicoils are at the bottom of the list of thread repair kits in terms of durability & strength. A one-piece insert like Time-Serts or EZ-loks works much better.

    Heli-Coils are used OEM by many, Campy seatposts for example. A threaded insert can be used as a repair for a Heli-Coil that fails. I consider threaded inserts to be the repair of last resort because it requires the most material removal. If installed correctly Heli-Coils work very well. I prefer the brand Recoil.

    http://www.newmantools.com/recoil1.htm

  14. #14
    Senior Member DannoXYZ's Avatar
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    Quote Originally Posted by ISeeDeadHuffies
    Heli-Coils are used OEM by many, Campy seatposts for example. A threaded insert can be used as a repair for a Heli-Coil that fails. I consider threaded inserts to be the repair of last resort because it requires the most material removal. If installed correctly Heli-Coils work very well. I prefer the brand Recoil.

    http://www.newmantools.com/recoil1.htm
    Yeah, I think the Helicoils would be OK. I'm just used to the more extreme repairs needed like head-studs/bolts that need 150-lb*ft torque. If the thin/thickness of the mounting plate doesn't allow for sufficient number of threads, a riv-nut may also work as well.

  15. #15
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    I checked out both Time-Serts and EZ-Lok and I've found a couple problems. With Time-Serts, the lip on the insert might interfere with the cable clamp washer's ability to efficiently clamp down on the cable. With EZ-LOKs, the outer diameter for their M5 threaded insert is an M8. That large of a hole would cut out a little too much metal in that little tab for my comfort. The "thin walled" insert in 10-24 (no metric) requires a 5/16 tap size, also a little too big for my comfort. Not alot of material would be left around the hole, and that worries me. Anyone know how big of a hole the Heli-Coil kit requires? Also, the material I would need to heli-coil/thread repair is only about 4mm thick. I think this also presents a problem.

  16. #16
    Senior Member Sci-Fi's Avatar
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    You need to use the recommended drill size. In your case, a 13/64 drill. The included tool should have the correct tap for the helicoil and it depends if you have a "free running" (tang) or "screw lock" helicoil inserts. Either one can be hand screwed into place or with the "tang" helicoils, the included tool can use the tang part to screw it in and snap off the tang.

    Could use a locking compound on the helicoil and newly tapped threads, BUT you would have to let it set up. Otherwise the bolt and helicoil might lock together and screw/unscrew as one unit. Not a good thing.

    Alternatives would be to buy a 1 mm thick steel metal sheet or ask for a scrap and drill and tap it for your m5 bolt and of course shape/cut it to fit...can use a regular nut as a template or just square cut it so you have a gripping surface for a wrench. Body shop "fold-over clips" or "bolt retainers" work (have to check clearances) and are thin enough ... pictures here: http://www.thefastenerwarehouse.com/...age/568857.htm , can probably find one that fits at your local auto parts store. If you have a knowledgeable aluminum shop nearby, they can shrink the hole so you can drill and tap it to the original specs.

  17. #17
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    Looks like I'll be ordering a heli-coil kit.

    Iseedeadhuffies-Thanks for the recoil suggestion. I'll be calling them monday.
    Dunwood-Thats a good idea, if I can find that particular fastener. My plan B.
    Danno-Thanks for the rivnut suggestion, I'll consider it if other plans dont work, and if I can find someone to loan me a rivet nut tool.

    EDIT: Thanks SCI-Fi. I'll check that out...Re-Shirinking the hole? Whaaa?

  18. #18
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    Here's an off-the-wall solution to ponder: fill the hole with a metalaized two part epoxy such as J-B Weld, allow it to fully cure (1-2 days) then drill and tap it. I've had good success with this product in other applications and the packaging says that it can be drilled and tapped. If it doesn't hold, you should be able remove the "insert" from your bolt with a wire brush and move on to a different solution.
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  19. #19
    Senior Member Sci-Fi's Avatar
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    Quote Originally Posted by rollsroyce
    Re-Shirinking the hole? Whaaa?
    It's almost the same has shrinking sheet metal except aluminum only needs to be heated up to about 550°F instead of red hot. Have to use smoothed faced flat hammer and wooden dolly to gently tap down the metal to "fill" the hole or make it smaller. Heating in spots (in your case, the area immediately around the bolt hole) will tend to make any metal expand/swell and by gently tapping the swelling metal down, the hole can be shrunk/partially filled with enough metal to enable you to retap the hole and maintain approx the same thickness. Here's a few links that may explain it better:
    http://www.bodyshopbusiness.com/bb/bb20650.htm
    http://www.tinmantech.com/html/repai...num_part_2.php

    Just to add: Could find/use a smaller inner diameter flat washer that you can tap.
    Last edited by Sci-Fi; 12-08-06 at 09:45 PM.

  20. #20
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    Update!

    Well, that was easy. Here are some pics and a little write up.

    I called around and found an M5x.8 Heli-Coil thread repair kit here in town (Houston, TX) at a fastener supply store called Coastal Fastener on 11th. Heres the kit:

    It came with around ten coils, an installation tool, and a tap. I was under the impression that the coils were more like inserts, with an outer thread that screwed into a hole and the inner thread being the one youre repairing. I learned that this is not exactly the case when I tried to screw an M5 bolt into the coil. The coil was much bigger and the bolt just slid in and out. I thought I had bought the wrong size, but after returning to Coastal Fastener, the sales guy assured me that I had the right size. Apparently, the coil is spring like and when threaded into the smaller hole the coil is forced to tighten up or shrink and it pushes out against the wall of hole its in, securing your new threads. Anyhow, the first step is to drill out the old hole. 13/64" was the required size according to the heli-coil kit:

    Next you use the supplied tap to cut new threads. I had a little bit of trouble getting the tap started nice and square, but it worked out just fine:



    Heres a shot of the coil inserts. They vary in length by a mm or two, so I picked the shortest one I could find since the thickness of the material is only about 4mm:

    None of my photos of the next step came out so I'll describe it as best I can. The coil inserts have a little tang reffered to in the instructions as the "driving tang" on one end:

    The installation tool included hooks on to this tang. You insert the coil, tang-side first, into your newly threaded hole. It takes a careful twist to engage the first thread with the coil, but once its engaged you just twist the coil into the threads with the tool. Be careful not to break off the tang during this process, theres a notch near the tang to make it easy to break off after installation. I broke two coils like this during installation, but theyre easily pulled out.
    A shot of the coil inserted into the hole. Abracadabra, new threads.

    trimming the excess coil:

    I also used these pliers to trim the tang off of the other side. The finished product:

    A working derailleur! I picked up a buttonhead screw like Dunwood suggested, and I'm very happy with the end result. Thats it. It was too easy. Thanks for the help everyone. And also thanks to DMC, who I bought this derailleur from and was honest and cool enough to supply me with the funds to buy everything neccessary to repair the derailleur after we both found out the anchor bolt hole was stripped.
    Last edited by rollsroyce; 12-11-06 at 06:37 PM.

  21. #21
    8speed DinoSORAs Ed Holland's Avatar
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    Very neat!

    ...and a great illustrated guide to the Helicoil process - thanks rollsroyce

    I used one of these kits (The Recoil brand I think) earlier in the year, and was a bit apprehensive about it (it was for a mounting bolt on my car's suspension ). In fact, it is very easy, especially if you have a little experience in cutting threads.

    Cheers,


    Ed
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  22. #22
    Senior Member BikeManDan's Avatar
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    Thanks for making the walk through. Never actually knew how it was done

    How much did the kit run you?

  23. #23
    hello roadfix's Avatar
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    Great job on the repair!
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  24. #24
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    Hey thanks guys. I thought it was funny that my camera crapped out during one of the most important steps, the insertion of the coil! The kit ran me $45.00 + tax. I meant to add that for future refernce, if anyone needs to do the same thing I'd be happy to pass the thread repair kit along. Theres 8 coil inserts left. I think M5x.8 is pretty common on bicycles so someone is bound to run into the same thing.

    Though I might need it back after its borrowed and a couple coils are used.

    The process was so easy that after I was done, I literally said to myself out loud "thats it?" I didn't think it would be worthy of a little write up, but wrote one anyway. Glad I could help!

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