Help! Broken headset cap bolt-head

Discuss light weight issues concerning road bikes & parts.
chunky
Posts: 3
Joined: Sun Dec 23, 2012 5:48 am

by chunky

I was assembling my new used Specialized tarmac and broke the bolt head that tightens the headset cap. So now I have a small bit of bolt poking out.
Image

I've tried to remove it with vice grips, but the material is to soft and crushes without moving the bolt.
Then tried to dremel a slot to turn it back with a flat-head screwdriver. Again, the material just gives out.

Now I'm afraid of working any more on it for fear of not having anything left for the LBS to work with.

Suggestions are appreciated!

Thanks!
Last edited by chunky on Sun Dec 23, 2012 7:19 am, edited 1 time in total.

by Weenie


lechat
Posts: 260
Joined: Thu Sep 30, 2010 3:32 pm
Location: S.E. TN

by lechat

Is it still holding the cap on? If so, drill it out and use needle nose vice grips to get a better purchase on the shaft. Caps are cheap.

chunky
Posts: 3
Joined: Sun Dec 23, 2012 5:48 am

by chunky

The pic wasn't showing up properly... is it now? Here's the direct link:
http://i.imgur.com/yfojw.jpg

Cap is already off. Just don't have much of the bolt shaft to grip on to. Or what I tried to keeps crushing. If I drill all the way through, does that tapered piece at the top where the bolt is threaded into come off?

TOflat
Posts: 156
Joined: Fri May 21, 2010 5:43 am

by TOflat

Image
Broken screw extractors. Commonly found in hardware stores and relatively inexpensive (Less than 20 bucks for a complete set like this)

http://www.youtube.com/watch?v=Z_6RUa0fH4U" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

In the video this muppet of an idiot taps the screw extractor with a hammer without actually holding the extractor itself, this is stupid and will wreck the broken screw more than it already is and you may lose that biting edge.

For the m5 screw you've broken, find a 1/8" drillbit, drill as close to the centre of the screw as you can. *Very carefully, not a lot of pressure, otherwise the bit will jump around and hit something unintentionally*

Once you've got a small pilot hole *Ideally 1/4" or more is nice, but not necessary, just enough for the screw extractor to bite into the material. Because the screw is so soft, the deeper that hole the better and the more material the extractor can bite into*

Tap the screw extractor into the hole lightly (NOT LIKE IN THE VIDEO! Small hammer, or the end of that adjustable wrench, just enough to dig the extractor in a little)

Turn LEFT or Counter Clockwise and gently bring out the screw.

If you believe there is a little corrosion or the screw may be seized, after drilling the hole, drip a little oil inside the hole and let it penetrate for a little while before attempting to extract the screw.

Hope this helps!

(Also, looking at the picture you've posted, take the dremel tool you have and see if you can flatten out the top of the screw or at least create a small point where a small drillbit can start making a hole, it helps to centre the bit while it's spinning so it doesn't flop around. I also advise you to not clamp on the head with a pair of pliers anymore, it will only damage the head of the broken screw further and create more of a headache)

em3
Posts: 887
Joined: Tue Dec 23, 2008 2:57 pm
Location: NYC

by em3

I have to ask, how does one break a top cap bolt? Preload for ur bearings should only require at most 2-3 Nm of torque. What were u cranking ur bolt to? EM3
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sungod
Posts: 1462
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

^^^this!

also, do what TOflat says

roselend
Shop Wrench
Posts: 165
Joined: Sun Sep 05, 2010 9:31 am
Location: Belgian border

by roselend

Hold on,
Is the expander itself fully tightened down? If so, thats too bad.

You probably already know this but just in case.
Please keep in mind that you cant remove these type of expanders by just loosening the bolt.
You're suposed to loosen the bolt slightly, keep the hex key in and give it a wack with a hammer to release the lower wig from the rest of the expander. Then the tension is gone and you can just pull it out of the steerer.

thisisatest
Shop Owner
Posts: 1980
Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

I'm with Roselend- try to get the whole expander out. Hopefully, the expander wasn't firmly tightened to begin with.
If you drill all the way through, you will not drill into anything but bolt. the threaded hole continues through the expander.
Back to getting the expander out, if you drill or dremel the bolt down just past flush, you may be able to fit the 6mm hex key required to loosen the compression plug itself.

TOflat
Posts: 156
Joined: Fri May 21, 2010 5:43 am

by TOflat

I don't advise doing that just to get the expander plug out. I've had to do this on one or two customers bikes at the shop. The expander plug is usually aluminum and any real attempt to extract it by force usually deforms the hex head to begin with. Also you have no recourse for getting the broken bolt out of the expander plug once you get the plug out to begin with.

Try drilling the small hole in the broken screw head first, don't worry if you cannot drill all the way through, it is not the point to do so in any case. You just want to be able to get the screw extractor in there.

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
Contact:

by eric

TOflat's directions for using the screw extractor are good, BUT be VERY careful about the force you put on the smaller extractors. They are hard metal and thus brittle. It is easy to snap one in half if you put side force on it. I have even snapped one by twisting it too hard- it made a nice spiral fracture. If you break it off inside the bolt you'll have a hard piece of metal in there that you can't drill out.

If you have a dremel you can use it to flatten the top so you can drill it without wandering off center.

chunky
Posts: 3
Joined: Sun Dec 23, 2012 5:48 am

by chunky

Thanks for all the helpful tips...
I have some questions though. I'm not familiar with what is inside the steerer tube..

From the "outside" in:
1) Headset Bolt
2) passes through the headset cap (which is off now)
3) Threads through the part in the pic - is this the "expander plug"?
4) ??? Or does it thread into something else further down the steerer tube?

And yes... I completely cranked it tighter than normal before the bolt breaking. i think the previous owner may have left off one headset spacer so there was play between the headset cap and the other spacers. I just kept tightening to make up for the play... and bam! the bolt broke.

The bolt is very difficult to move with vice grips/pliers/flat-headscrewdriver.

Last resort... if the expander plug is completely expanded and I destroy the bolt, can I just chop off the steerer tube? It's at maximum length now and I can probably afford to cut it down....If so, how deep is the expander plug (ie, how much can I cut off)? Or can I drill the bolt all the way through?

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
Contact:

by eric


sungod
Posts: 1462
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

if there was a spacer missing the top cap would have bottomed out on the expander rather than pressing on stem/spacers, sounds like the reason

tbh with the expander type i've used, if you have to make the top bolt more than finger tight, something is wrong

expander plugs may be quite deep, depends on the model but around 50mm is possible, so cutting the steerer isn't a good option

often the bolt goes into a hole that has a hex recess, with the bolt out, you can put a hex key in to tighten/loosen the expander, from the picture it's hard to tell, but it doesn't look like that type

i'd go with the screw extractor method, you can start with a small pilot hole as it may be easier to control, especially if you use a dremel/similar drill, then use a larger bit to get the correct size for the extractor

timzcat
Posts: 315
Joined: Thu Sep 30, 2010 5:50 am

by timzcat

Screw extractors will do the trick but your best course of action is to get a reverse drill bit for drilling it out. Typically using a reverse drill bit to perform the drilling will in and of itself loosen the bolt so you won't have to resort to the actual extractor.

em3
Posts: 887
Joined: Tue Dec 23, 2008 2:57 pm
Location: NYC

by em3

chunky wrote:Thanks for all the helpful tips...
I have some questions though. I'm not familiar with what is inside the steerer tube..

From the "outside" in:
1) Headset Bolt
2) passes through the headset cap (which is off now)
3) Threads through the part in the pic - is this the "expander plug"?
4) ??? Or does it thread into something else further down the steerer tube?

And yes... I completely cranked it tighter than normal before the bolt breaking. i think the previous owner may have left off one headset spacer so there was play between the headset cap and the other spacers. I just kept tightening to make up for the play... and bam! the bolt broke.

....

Last resort... if the expander plug is completely expanded and I destroy the bolt, can I just chop off the steerer tube? It's at maximum length now and I can probably afford to cut it down....If so, how deep is the expander plug (ie, how much can I cut off)? Or can I drill the bolt all the way through?


Chunky, it sounds like you are in WAY over your head on this one and need some professional help (no offense, just being realistic based on the damage so far and the questions you are posting)...remember that you are working on a carbon steertube so you will want to be extra careful not to damage the tube or you are in for a new fork as well. There is no work around to getting this done right if you want to salvage your fork....and only the proper tools already recommended by others above, together with proper skills, will get the job done correctly.
EM3
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by Weenie


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