Solutions for a damaged rear mech mounting bolt?

Chips Lovell

Through my own stupidity I managed to strip the head on the mounting bolt for a rear mech.

Bolt was a Torx 25 but when that didn't fit in (possibly because of dirt) I thought I was mistaken and used a Torx 20, which stripped the head.

I'm now left with a rear mech that is, to all intents and purposes, stuck on the hanger. The reason I was taking it off was that the hanger is slightly bent.

So, any ideas on what to do? I reckon I can get a new bolt, but how to get the mech off the hanger and extract the old bolt is currently beyond me.

Raam

Bring it to a bike shop and get them to do it.

Chips Lovell

I'm considering that too. But given that they'll have to order parts in etc., it probably means leaving the bike in for a few weeks, with no guarantee they'll have any success in getting the thing off.

doozerie

Some possible approaches that spring to mind:

* You can buy stuff that helps screwdriver tips to gain some grip in semi-stripped screw heads. It's basically an abrasive in a type of gel. Depending on how much torx head is left this might work with the right torx head to grip the bolt head.

* Can you force an allen key into the bolt head? If you have one of a suitable size then it might get enough bite in whatever is left of the torn torx grooves (if any) to grip. Or use a smaller allen key and stuff in bits/shims of metal/wood/plastic between the alley key and the sides of the torn opening to allow it to grip. If that doesn't work with the hanger on the frame can you remove the hanger and gear cable and try it off the bike? That would allow you to do various "delicate" things reasonably safely, like apply a hammer to the allen key (or shims, or screwdriver, or whatever fits and will bite), or clamp bolt and allen key in a vice to try to squeeze the allen key in.

* Remove the hanger and cut the hanger off the derailleur bolt. The hanger is probably softer and therefore easier to cut than the bolt itself.

* If you have a sacrificial allen key you could glue it into the torx head and simply unthread the lot when the glue is dry. Make sure the allen key is long enough not to catch on the derailleur body though, obviously.

* Drill a hole in the opposite (non-head) end of the derailleur bolt, screw in a bolt or a strong screw, and hopefully by "tightening" that bolt/screw the motion will unthread the derailleur bolt from the hanger.

Peterx

doozerie wrote: »

* Drill a hole in the opposite (non-head) end of the derailleur bolt, screw in a bolt or a strong screw, and hopefully by "tightening" that bolt/screw the motion will unthread the derailleur bolt from the hanger.

http://www.brokentap.com/easy-outs.html

Easy outs are your friend here. Drill a hole in the middle of the bolt and easy out.

macnab

If you can cut a slot across the head of the bolt you could use an impact driver with a flat screw driver head.

Chips Lovell

Head is recessed into the dérailleur body, so that rules that one out.

doozerie

Peterx wrote:

Easy outs are your friend here. Drill a hole in the middle of the bolt and easy out.

I've tried such extractors before, though on narrower bolts/screws than a derailleur bolt, and they have yet to work for me. I was contending with hardened steel though, so certainly not a good place to start! In principle they are very good, but in practice they require a very steady hand, a good quality drill bit, and a decent drill too, to drill the initial hole accurately as it's quite tricky. Extractors have become the last option I look at due to my past experiences.

Also, using an extractor requires drilling into the head of the bolt where you may have little visibility of how close your drill bit is getting to the outer diameter of the bolt itself, so there is some danger (depending on diameter of drill bit) that you might damage the derailleur bolt housing. When you have easy access to the other end of the bolt then you potentially have better visibility of where the drill bit is going. Plus, once you've drilled the a hole in the far end, you can use any suitably sized bolt or screw (bolt being better though I reckon as it'll be more robust than a screw) to thread into the hole, whereas the extractor is relatively brittle and may not stand up to much punishment.

Chips Lovell

Thanks doozerie. So far I like the sacrificial allen key idea best. Although knowing my luck the key will break at the bend.

Does anyone know how you ordinarily get these bolts out? Exploded diagrams are here on page 34. Is it a case of popping the seals and pushing it out from the back?

Cayo

Those extractors mentioned above are a bit crap to be honest, any time I have tried to use them they have just sheared leaving me with a much harder job to remove the stud. This was on seized bolts/studs so prob a bit more difficult to remove.

Two methods I have used for rounded/stripped allen key head.

Using a set of these

or probably a simpler solution for you is to get the next size up of torx and force it into the rounded bolt head which might provide the grip required to open the bolt. A socket style torx is best for this.

having said all that, I have used these methods on cars with a liberal application of heat (gas torch) and persuasion (hammer) so might be a bit rough for a fancy carbon frame!

doozerie

ScrewGrab is one version of the grippy stuff I referred to above. It may not work very well with the likes of a torx head though, it really depends on whether there is anything left to grip in the first place.

Potentially anything gritty that remains in place will work too, but the only ones that spring to mind are ones that may be just as hard to source locally. You could try the likes of a gritty hand cleaner in a pinch (Lidl sell tins of it - works great at cleaning up your hands after wrestling with the bike ), likely to be nowhere near as effective but if it added any grip at all you might be lucky and find that it was enough.

doozerie

I'd assumed that the bolt was held on by a circlip or similar, like the Shimano ones I've looked at are done, but that exploded diagram seems to show something else for the Chorus and upwards models and I'm not sure what that is. If yours is one of those models then I'd be inclined to avoid anything like drilling the non-head end of the bolt for fear of creating other problems there.

Although the sacrificial allen key is a relatively clean option I think I'd go the hacksaw route myself as it could prove to be fairly quick. It depends on whether there is clearance to use the saw without hitting the mech housing though obviously, plus once you've started on the hacksaw option you are pretty much committed to it since you'll have potentially weakened the hanger so much that you'll have no solid bit of hanger left to grip if you subsequently revert to trying to unthread the bolt. So I guess that if you are confident that a hacksaw will do the job cleanly with your hanger, I'd go with that, but if you had any doubt at all I'd avoid it entirely.

Chips Lovell

It's an Athena mech, so doesn't seem to be constructed same as the Chorus and upward ones.

doozerie

I just did an online check for info on how to remove the bolt and found this weightweenie thread (and also this other thread). Since yours is an Athena the info on those threads may not be relevant but the weightweenie thread has a photo showing that the non-head end of the bolt on a Super Record mech has a Torx head itself. If that was in the Athena model too (unlikely I imagine but worth a quick check) you could potentially use that to unthread the bolt.

doozerie

Oh, and because the Athena seems to use a clip to hold the bolt on, you should be able to prise/hammer that off once you have the hanger removed.

lennymc

Id bring the lot to an engineering firm who should have the tools and equipment to remove it without damaging it, and without you having to buy new tools.

doozerie

lennymc wrote:

Id bring the lot to an engineering firm who should have the tools and equipment to remove it without damaging it, and without you having to buy new tools.

Pffft, that kind of thinking results in no hammers at all ever being swung with wild abandon. And therefore no bashed thumbs. And without the odd belt of a hammer to remind them of their relatively low place then thumbs will get all uppity and their already exaggerated notions of their own importance ("we are opposable you know, sure aren't we only fabulous!") will lead to all kinds of trouble. So teach your thumbs their place, pick up a hammer and let rip!

Chips Lovell

Thanks, that's very useful. I'll do some more investigating of it armed with all this new info.

lennymc

doozerie wrote: »

Pffft, that kind of thinking results in no hammers at all ever being swung with wild abandon. And therefore no bashed thumbs. And without the odd belt of a hammer to remind them of their relatively low place then thumbs will get all uppity and their already exaggerated notions of their own importance ("we are opposable you know, sure aren't we only fabulous!") will lead to all kinds of trouble. So teach your thumbs their place, pick up a hammer and let rip!

I'm terribly lazy.

I once swung a hammer and hit myself in the face. True story.

doozerie

lennymc wrote: »

I once swung a hammer and hit myself in the face. True story.

That'll be your thumbs testing their boundaries. You've clearly been too easy on them.

Peterx

Pah, I snort in brave keyboard warrior style at the easy out haters on this thread, Down With Ye All, Haters! in capitals!!

The easy outs work fine in this case.
The bolt isn't seized in place.


OP, If you can get into Dublin city centre pm me and I'll provide;

the drill
the drill bit
the easy out - the very easy out that has performed this very task before, a easy on the eye out it is too. In fact when I get a chance I'll take a photo of it and add it to the images of beauty thread!

and with a suitable guarantee of you not giving out if it all goes wrong I'll also provide the steady hand.

can't say fairer then that!

Peterx

doozerie wrote: »

I've tried such extractors before, though on narrower bolts/screws than a derailleur bolt, and they have yet to work for me. I was contending with hardened steel though, so certainly not a good place to start! In principle they are very good, but in practice they require a very steady hand, a good quality drill bit, and a decent drill too, to drill the initial hole accurately as it's quite tricky. Extractors have become the last option I look at due to my past experiences.

Also, using an extractor requires drilling into the head of the bolt where you may have little visibility of how close your drill bit is getting to the outer diameter of the bolt itself, so there is some danger (depending on diameter of drill bit) that you might damage the derailleur bolt housing. When you have easy access to the other end of the bolt then you potentially have better visibility of where the drill bit is going. Plus, once you've drilled the a hole in the far end, you can use any suitably sized bolt or screw (bolt being better though I reckon as it'll be more robust than a screw) to thread into the hole, whereas the extractor is relatively brittle and may not stand up to much punishment.

PAH!

Chips Lovell

Peterx wrote: »

OP, If you can get into Dublin city centre pm me and I'll provide;

the drill
the drill bit
the easy out - the very easy out that has performed this very task before, a easy on the eye out it is too. In fact when I get a chance I'll take a photo of it and add it to the images of beauty thread!

Thanks Peter, I may well take you up on that.

Thanks again to everyone for the advice. I've decided on a plan of action.

1. Order new mounting bolt (made enquiries with Velo Tech today) and wait till it arrives.

2. Try to get bolt out, first with allen bit, then with drill bit.

3. If that fails resort to sawing hanger off and going at it from the back.

4. And if that fails, give it to a shop and let them at it.

Seaneh

https://www.youtube.com/watch?v=MaCYyL4UJAA

Swap "screw" for "bolt" and away you go.

bcmf

Vlad,
I have the remains of a 10 sp Veloce RD that still has the bolt.
If its any use to ya just shout and its all yours!