Bicycle Mechanics - Stripped F. Derailleur Cable Anchor Thread
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10-18-03, 07:29 PM
I managed (through my own stupidity) to strip the thread on the cable anchor bolt hole on my front derailleur (Suntour Cyclone M-II circa 1983). So now, I can't fasten down the bolt tight enough so that I can apply pressure to the cable...it just slips out when I move the lever.
My question - is there any way to fix a stripped thread like this? I have read about using Teflon plumbers tape to stop things from squeaking. Would a few extra layers of this help with my problem by "filling in" the threads? I'm doubtful, but it's the only option I can think of, short of re-drilling a larger hole and re-threading it, which I would like to avoid if possible (how easy is this to do on this type of aluminum?) Any other options, or should I just start looking to buy a replacement derailleur? If so, how do I tell what types will be compatible with what I have?
Thanks for any and all replies!
10-18-03, 07:39 PM
My question - is there any way to fix a stripped thread like this?
Your answer - re-drilling a larger hole and re-threading it
Investigate an SAE size thread slightly larger than the current metric bolt (or vice versa), you might get away with only running a tap and not have to drill the hole.
BTW - Be sure to use a fine, not course thread.
Best wishes, it worked for me when I did the same to my r'der.
10-18-03, 07:53 PM
You can drill through the hole and simply use a bolt, washer, & nut to secure the cable......or, you can maybe find a replacement here:
Rethreading a slightly larger hole should be trivially easy. You need to ID the screw size now used (probably 4 or 5mm x 0.8mm) and find a replacement screw the right length and configuration. The clamping washer may need to be drilled out as well. Once the screw is found there are standard tables of drill sizes used to drill a hole for a given size tap. Taps in the right size will be $2-4 depending on source, or as low as $1 from a few sites. Try to find a screw with an allen head for convenience. Do NOT use straight slot screw (unless hex head) and avoid phillips head as they tend to strip easily. Robertson head is great but few bike tool kits have the tool. You will need a tap holder, it is amazingly easy to cross thread the start on taps, though Al is not much of a problem, you can't do it with a wrench. Taps have square ends so a brace might work in a pinch. You do have a brace as in brace and bit (obsolete hand powered wood drill.)? Steve
Just buy a new one. They are not too expensive and
fairly common on e-buy.
Here are 2 that I found today. both less than $20.00, 15 should be
close to winning bid.
10-20-03, 12:07 PM
Look close at the der., quite a few front ders. have a nut swaged in. On these you can rest the arm against a vice opened just enough to let the nut pass and tap it out then tap a new one in.
11-02-03, 08:44 PM
Hi guys, thanks for all of the above advice. However, I've been putting off doing anything about this, and was thinking it's about time I did. Since I'm not too sure about doing this myself (don't want to ruin anything any more than it already is...) is it reasonable to take it to a shop for this type of job? Do they have the tools to rethread or whatever is necessary? I guess I could call the LBSs and see what they say, but I'd like your opinions too!
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