# Helicoil "How-to"? for Derailleur Hanger, Help!



## jvanv8 (Nov 14, 2006)

I managed to strip out the derailleur hanger bolt threads on my frame. I have extra bolts but it appears that the frame threads are stripped.

The hole is extremely small and probably only has 3 "threads" for a bolt to bite into.

- Is it possible to do a Helicoil job on this? I don't know anything about heli coil except that I've heard it mentioned in forums when bolts are stripped.

- Can I fix the thread with a helicoil kit myself? or do/should I have a pro do it?

- How are these things sold? Do I get a kit and find the right size or do I order the exact size I need ahead of time?

- How can I determine which size the bolt is?


OR ____
- Do I get a tap and retap it? (I have no idea how to do this either but maybe it's easier)

Thanks guys!
John


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## DERMotorSports (Nov 21, 2007)

First, what material is the frame? Is the rear derailleur replaceable?

Assuming it is steel or Al and NOT replaceable, the next question is how mechanically adept are you? This is important - cause a screw up here can be bad; so if not very adept at all, take it to a pro. If adept, you'll need to size the hole - rd is standard so no issue there. Then you'll have to purchase the kit from HeliCoil or a decent hardware store - when in doubt, try http://www1.mscdirect.com/CGI/NNPDF...229472&PMITEM=00068361&PMCTLG=00&PMT4TP=*LTIP. 

The kit will contain everything you need except a drill. Just follow directions or call here: 770.631.0125 

The HeliCoil site is at:http://www.emhart.com/products/helicoil.asp

Dan Law
[email protected]


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## kidd546 (Nov 3, 2007)

If there is enough metal left to re tap you can just run a tap in the hole. More than likely there is not enough metal left.Wheels Manufacturing has repair kits that have you drill the hole out then place a nut through the back side and bolt the dérailleur in place. But first check and see if your frame has a replaceable hanger, this is the easiest way.


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## jvanv8 (Nov 14, 2006)

The frame is aluminum and yes, the derailleur hanger is replaceable. The screw is the one that holds the hanger to the frame. The bolt goes through a hole in the hanger and secures inside the frame... which is stripped. It's super small and probably can't protrude too much out the end since it would interfere with the cassette.

As far as mechanical knowledge.. I basically have done all my own bike maintenance for the past 10 years without going to a shop... but I've never dealt with stripped bolts before.

Thanks for the link on the helicoil kits. Great resource.

So is it confirmed that helicoil is what I need to do and not tapping a new thread?


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## android (Nov 20, 2007)

jvanv8 said:


> The frame is aluminum and yes, the derailleur hanger is replaceable. The screw is the one that holds the hanger to the frame. The bolt goes through a hole in the hanger and secures inside the frame... which is stripped. It's super small and probably can't protrude too much out the end since it would interfere with the cassette.
> 
> As far as mechanical knowledge.. I basically have done all my own bike maintenance for the past 10 years without going to a shop... but I've never dealt with stripped bolts before.
> 
> ...


I'm not sure that you would need a helicoil here because it doesn't matter if you go to the next size bigger screw to hold the hanger to the frame. Just find out what the next larger screw is and drill and tap to that size and then bolt the hanger back to the frame. 

You have to use a helicoil when the bolt HAS to match an existing bolt such as a derailleur bolt to hanger connection. Since that is standard, you can't go to a bigger size.

A specialty fastener store can help you out. Most major cities will have one. Look under fasteners in the yellow pages and take them your broken stuff. They'll find you something close, but you may have to file or grind off the protruding end to clear the cassette.


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## Cheers! (Aug 20, 2006)

Yes it is possible to fix the threaded hole on your frame via helicoil. I would let a pro do it. The helicoil kit (which contains, correct drill size, helicoil, helicoil tool) will run you what it would cost a good bike shop to fix. The size is probably anything from an M4 to M6 metric thread fine. 

Personally I would fix it rather than drill out the whole and convert it to a through hole for a nut bolt arrangement.


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## Touch0Gray (May 29, 2003)

my experience with helicoils is that they work best in a deeper, close bottom hole. correct me if I am wrong but to put a helicoil in, you drill the hole out to the "next size" larger and tap the hole to allow the thread on the outside of the helicoil to thread into the new, re-tapped hole. The bottom of the coil has a "tab" that the inserter catches to screw the coil into the new hole from the bottom, (it resembles a slinky" and winding it in from the top causes it to expand and NOT go in properly.
The inside of the helicoil is the matching thread for the old bolt. What will hold the helicoil in place while the bolt is screwed back in to it, particularly if there are only like 3 threads holding it in?

all my bikes have a brazed or welded der. hanger, but my son's mtn bike has a bolt on hanger, and there is a bolt, with the head on the inside (wheel side) and a lock washer and nut on the outside. would that work for you? Even if you had to grind the head down a bit to avoid catching on the cassette.....


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## Cheers! (Aug 20, 2006)

At work (aerospace engineering) we use helicoils in similar applications. The number of threads engaged is a lot more than 3 since it is a fine thread metric fastener. Typically the thickness of the dropout which the hanger bolts onto is 1/4 to 3/8" thick. Good enough for atleast 6+ threads to be engaged. I have not seen how bicycle shops install said helicoil into small threaded holes such as this application. But we apply helicoil primer that dries to help "glue"/secure the helicoil to the new tapped hole. Certain types of epoxies work as well. Again your mileage may vary, and different companies make helicoil kits/types for different applications. Surf around for one that is adequate for your needs. Or just drop the bike off at your most trusted local bike store with a 6 pack of beer.


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## Touch0Gray (May 29, 2003)

i was wondering if epoxying the coil in would be of any benefit...


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## Cheers! (Aug 20, 2006)

Touch0Gray said:


> i was wondering if epoxying the coil in would be of any benefit...


It can. Be careful which you choose because some are too "runny" some are too "thick" causing the epoxy to bleed through to the internal threads. Less is also more in this case. Use sparingly, and also make sure everything is cleaned with strong solvents to remove oils from fingers etc.


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## jvanv8 (Nov 14, 2006)

Hmmm, I wonder about the epoxy idea too, although a bolt is more functional. But really the hanger doesn't see much stress at all. It just keeps it in place and keeps it on the bike when you remove the wheel.

Since pictures are always better, here are a few... the frame in the picture is identical to the frame in question (I had 2 frames but the one in these pictures was hit by a car  )




























Its a road frame so keep in mind that the derailleur tab is very thin.

Finding a specialty fastener store might be tough... I'm currently in Europe so I'm not sure how available some resources may be. I can always import a helicoil kit and the drill and tap is easy to find anywhere, right?


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## DERMotorSports (Nov 21, 2007)

Be very careful if using epoxy - it's pretty damn permanent. If done right it is great; if wrong will be next to impossible to ever remove and possibly look crap. In this case, I would use an easily redoable solution like standard HeliCoil. Another solution is "ThreadSert" but more expensive. Oh yeah, if buying the Helicoil kit, all the ancillaries are included and you need only provide the electric drill (taps, tools&c are in the kit).


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## Touch0Gray (May 29, 2003)

ok, I'm confused...that picture looks to me like it is the rear dropout that is bolted on....does it hold the wheel in as well as the der.?


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## android (Nov 20, 2007)

From the photos, I see no need to spend money on a helicoil. Just tap the hole to the next bigger size and get the next bigger screw. You use a helicoil when you have to have the same size hole. There is no requirement for that here.


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## DERMotorSports (Nov 21, 2007)

Oh yeah, IF you do go the HeliCoil route. There are different lengths of coils AND the coils can be cut shorter so as to be flush with the surroundings once installed - we do this often to custom fit. Typically we only use HeliCoil in non critical fasteners (just our policy has nothing to do with litigation just our beliefs).


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## dougfdny (Oct 14, 2006)

*dropout savers*

this will solve your problem.any reputable shop should have em...or get them here..http://www.wheelsmfg.com/products.php?cat=tools&prod=framerepair


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## litespeedf1 (Jan 23, 2007)

Last I checked, Loctite was used to secure the helicoil in place The specific type Loctite depends on the specific application. Check with Loctite website.


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## Cheers! (Aug 20, 2006)

dougfdny said:


> this will solve your problem.any reputable shop should have em...or get them here..http://www.wheelsmfg.com/products.php?cat=tools&prod=framerepair


That looks like the wrong product for the intended application. The link you have posted looks like it is meant to fix dropout/dérailleur hangers that are not replaceable. The original poster's issue is that he is unable to mount a new dérailleur hanger onto his frame because the threads for the screws that secure the dérailleur hanger are damaged.


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## Thommy (Sep 23, 2003)

I'd go with what Android has to say. Next size up and a flush mounting screw will get you riding again. Pretty common break (glad these do what they're designed to do), easy fix. I've seen a lot of this with mountain bikes. Kudos to dougnyfd for the info on wheelsmanuf dropout saver (couldn't remember the name of the product). Definitely locked that into my favorites. If you used an epoxy between the frame and dropout (for lack of a better word) the breakaway feature might not happen and you might eat a derailleur in the event of an accident. Hope you can resolve the issue. By the way, what kind of frame is this?


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## jvanv8 (Nov 14, 2006)

Hi Thommy, the frame is a FetishCycles but I think other companies also use/brand the design









Actually the hanger did not "work as designed" (meaning the hanger didn't break off in some catastrophe)... it just came loose and I tightened the screw a little too much (which actually wasn't very much). With so few threads and soft aluminum it's easy to do I guess.

I'm going to see if I can find the translation for a "screw tap" to see if I can locate one around here.


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## litespeedf1 (Jan 23, 2007)

OP, If the threads in the bikes dropout are stripped, then using a helicoil might be the 'cleanest looking' fix. I know that the threaded bolt hole is only holding the hanger in place, but drilling and tapping for a larger bolt might have you searching for a larger bolt that could be very difficult to find. I think that the existing bolt head is the tapered type, probably specifically tapered for your type of hanger. If you know you can get a larger bolt to work with the hanger you have, then go with it. Using a 'Flat bolt' and nut could work if the bolt head or nut won't interfere with the chain riding on the smallest cog, but will probably not look too 'clean'. I'm attaching a link to the Helicoil site. http://www.helicoil.in/helicoil.htm#hi Again, if you decide to go the helicoil route, you can loctite the coil in place, this will result in a very nice looking and solid fix to your problem. BTW, if you use new fasteners in your repair, make sure they are stainless or titanium or plated so they won't rust or corrode.


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## jvanv8 (Nov 14, 2006)

hmmmm, yes, the bolt has a tapered head (forming a "V" side profile). Would it be hard to find the next size up with a tapered head? If not, maybe the helicoil option is better.

The bolt&nut option won't work... the distance between the frame and the chain/cassette is very small.


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## android (Nov 20, 2007)

jvanv8 said:


> hmmmm, yes, the bolt has a tapered head (forming a "V" side profile). Would it be hard to find the next size up with a tapered head?
> 
> The bolt&nut option won't work... the distance between the frame and the chain/cassette is very small.


No, it will not be hard to find the next size bigger bolt with a countersunk head and in the right length. They are very standardized. 

Technically what you have is called a countersunk socket screw. The one already in your bike is mostly likely an M4 or M5. Just go the next size up. The head will be 2mm wider. It will fit in the counter sink. It might stick out ever so slightly, but it will not be a problem.

Just go to the fastener store and tell them exactly what you want.

Example: I'd like the shortest M5 countersunk socket screw you got or a countersunk machine screw if you don't have a socket screw.

While you are there, get a nut to fit it. That will help if you need to cut off any.

This is a good reference site.
http://www.metrication.com/engineering/fastener.htm

Don't make a mountain out of this molehill.


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## jvanv8 (Nov 14, 2006)

Thanks android, great to know! Definitely need to brush up on my hardware knowledge  That site will come in handy. 
For making the new hole, I need a tap... is this basically just a special drill bit that coincides with the size of the screw or is it a special drill (electric, manual? / inexpensive?)?
I was able to find an adjustable tap wrench 1/16"-1/4" but how does this figure with M4/M5 sizes?

Sorry for all these questions but I don't speak the native language here... it's ok in the bike shop since I always know what I want but in a hardware store I'd be hopeless without prior knowledge.


> I'd like the shortest M5 countersunk socket screw you got or a countersunk machine screw if you don't have a socket screw.


Online translation tells me I need to say:


> Chtěl bych do téže míry člen určitý zkracený M5 heslo důlek závit tebe mít či jeden heslo stroj závit -li tebe činit ne mít jeden důlek závit.


Which when you put back into the translator to see the english again to verify you get:


> would like the shorted M5 watchword socket screw you hold or a watchword machine screw li you amount no hold a socket screw.


*actually this is one of the best backward translations I've ever gotten, it almost makes sense!

I might end up with a monkey wrench.


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## Thommy (Sep 23, 2003)

Cool. It would be a shame not to get your bike back together. Wonder if the screw has a 82 or 100 degree angle? Anyway, hope you get her fixed soon. Let us all know how she came out.


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## android (Nov 20, 2007)

Take your old screw with you. They can measure it and get the next size up.

You will need a drill bit and a tap. The tap will be the same size as your new screw, such as M5. Get fine not coarse threading for the screw and tap. 

You'll need a T handle for it. There will be an exact size drill bit that corresponds to the tap. The fastener store will know all this.

In the US at Home Depot, a small tap is < $5 and a T handle is another $5. Sometimes the tap is shrink wrapped on a package with the right size bit. Very handy.

There is special oil for tapping. You don't need it, this is low speed on Aluminum. Use chain oil, Canola oil, baby oil, whatever is handy. 

1) Enlarge the existing hole with the drill bit. I would probably put the bit in the T handle and do it by hand. Al will drill pretty easily. If not use a power drill. Just keep it straight and square as possible. Squirt a little oil on it while you're drilling.

2) BY HAND, and with another squirt of oil, start the tap in the new hole. Keep it straight and square. 2 turns forward then 1 turn backwards until it runs all the way through. Then take it out. You now have new threads.

3) Clean up the metal shavings and bolt the hanger on with the new screw. Remove the screw and file off the screw if it too long.

4) Go ride.


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## curlybike (Jan 23, 2002)

Thommy said:


> Cool. It would be a shame not to get your bike back together. Wonder if the screw has a 82 or 100 degree angle? Anyway, hope you get her fixed soon. Let us all know how she came out.


All metric flathead screws require a 90 degree countersink, the next larger screw will stick up above the surface that is countersunk, so the OP will have to use a countersink to make the countersunk hole deeper and bigger around so that the head will go flush. If you grind off the top of the screw, the hex for the key may be to shallow and the key may ruin the hex.


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## jvanv8 (Nov 14, 2006)

Ok, after some more hunting, I found that Tap Wrenches have a few different styles, "ratchet-type", "chuck-type", "chuck-type slimline". The ratchet-type is around $50 so probably the chuck-type is better.
Here are a few that I found... does the number mean that it fits all "M" sizes in the range?
Kennedy M2.2-M5 Chuck Type Tap Wrench-Slimline
Kennedy M3.5-M6 Chuck-Type Tap Wrench-Standard
Both are about $10.
but are these the actual tap bits? It's about $30.
... err... I think I'll have a friend ship the stuff from Home Depot over 
Thanks for the directions, I'm sure it will help me and other folks who search the forums for tapping techniques that don't involve beer... well, at least not until after.


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## android (Nov 20, 2007)

Yes, those are size taps that will fit. The kind you want is called "cheapest".

Thats probably a tap for some monster automated production machinery. Move along, these are not the taps you are looking for.

The kind you want looks like a screw with a squared end, only with some 4 or 4 slots up the sides to do the cutting. A single one should cost you a few bucks or euros or whatever they spend there. Here's a picture of an entire tap & die kit.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=39384


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## litespeedf1 (Jan 23, 2007)

OP, Here's a link to a fastener website http://www.boltdepot.com/dimension.aspx?cc=25&cs=83&cm=19. It seems that your existing countersunk socket screw is a 4m or 5m. Find out its exact dia. and go one size larger, say a 6m fine thread. Once you know what size machine screw you're getting, order the corresponding tap and drill set. Be patient, and then have a cold one to celebrate your fine work.:thumbsup:


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