Head cap bolt sheared

[Snorrarcisco]

Right I did a quick replacement of my stem and as I was tightening the head cap bolt the git the sheared it self off

It is a carrera crixus. The bolt felt rather weak to be fair and this is a second hand bike. I set the torque to the right pressure and as it clicked once just undid the sides, I did check and the torque was right for it.

Now to replace it do i just drill it and then remove cap and with pliers undo the bolt or is it more technical??

 

[Tim Hall]

Not sure what you mean by "undid the sides". Drilling the head off should work, allowing you to pop the cap off. You'll be left with the stub of the bolt screwed into the starfangled nut, which is a fitting an inch or so inside the steerer. With luck, as the bolt is no longer under tension, it should just spin out, with the help of a pair pliers.

 

[graham bowers]

It would be good if you could post a photo of the problem. If the cap head screw that compresses the head set has sheared, why can it not be just lifted out? If it has sheared and is still in situ, it will just turn if you try to drill it anyway. I wouldn't be reaching for a drill just yet until the detail of the problem is fully understood.

 

[Broadside]

It would be good if you could post a photo of the problem. If the cap head screw that compresses the head set has sheared, why can it not be just lifted out? If it has sheared and is still in situ, it will just turn if you try to drill it anyway. I wouldn't be reaching for a drill just yet until the detail of the problem is fully understood.

Indeed. I wonder if the star fangled nut has just pulled free rather than the bolt shearing.

 

[Citius]

You don't need a torque wrench on the head cap bolt, ffs - just nip it up.

 

[graham bowers]

You don't need a torque wrench on the head cap bolt, ffs - just nip it up.

Not everybody knows what half a turn off stripped feels like ;-)

 

[graham bowers]

Indeed. I wonder if the star fangled nut has just pulled free rather than the bolt shearing.

Or maybe the thread has stripped, not sheared.

 

[Citius]

Not everybody knows what half a turn off stripped feels like ;-)

You may have been joking, but the stem cap bolt works on being about 'finger tight', nothing more...

 

[Snorrarcisco]

I will try to get a pic but in the lack of it if I insert the Allen key it has no purchase so maybe the term is really like graham said and its stripped

will try to get a pic when i get home.

 

[raleighnut]

All the head cap bolt does is adjust the preload on the steering head bearings, once the stem is tight you can remove it as it isn't actually doing anything other than covering up the hole in the steerer.

 

[graham bowers]

This pic would really nail down exactly which screw has the problem, but would not help to identify if its stripped or sheared.If it was sheared then the head is no longer connected to the bit of thread that is engaged with the star-fangled-nut. Turn the bike upside down and give it a wiggle and it would probably drop out, or find some was to pull the screw. A stick and blu-tac in the hex for example. If it's stripped. the threaded part of the screw will still be engaged with the star-fangled nut but won't screw out without help, as the thread will be destroyed. The first thing I'd try is to improvise something to push up the fork steerer tube from below to put an upward force on the end of the screw (wheel off) and try to unscrew it whilst pushing on the end of the screw. A push may help it enough to then get a pair of pliers of mole wrench on so you can pull from above, whilst unscrewing. Hope this helps.

 

[Snorrarcisco]

I can safely say that the head cap is not moving at all. So i believe it is stripped but I will ensure i get a pic. I been looking and people say one needs to get tools for it but a drill should do the trick i hope hehe

 

[graham bowers]

If the thread is stripped I would expect the screw it to rotate somewhat freely, which I suspect is what you mean when you say it has "no purchase". That being the case, I expect it will spin when you engage a drill bit, so the drill will not, err, drill. Before resorting to drilling, I'd try what I posted at 12.41 and will elaborate on below.

If it is stripped, it will only be the portion of thread on the screw that is engaged with the nut that is damaged, the bit of screw poking out the bottom of the star-fangled-nut will be undamaged at this point in time. Whether the nut is stripped as well I can't guess, it depends how hard it is compared to the screw.

A stripped thread can sometimes be persuaded to unscrew if it gets a little help, in this instance a push on the bit of screw poking out the bottom of the star-fangled-nut. Take the front wheel off, turn the bike over and shine a torch up the steerer tube of the fork. You should see the end of the screw poking through the bottom of the star-fangled-nut. What I am suggesting is to push a rod or dowel up the steerer tube in order to put a force on the end of the screw and simultaneously try to unscrew it with an allen key. If it doesn't work, its probably worth tapping (in the sense of light hammer blows, not tapping a thread) the rod to "persuade" the threads to engage.

If you do have to drill, start with a small drill and work up in size gradually. A 5mm drill may just remove enough metal to allow the screw head to be removed, but will not engage with the internal hexagon of the cap head screw.

Good luck and please let us know how you get on.

Graham

 

[Snorrarcisco]

head cap

• Snorrarcisco
• 14 Dec 2015
• 1

this is the ofended head bolt

 

[Arrowfoot]

View: https://youtu.be/vyx-QoP3IsI