Help! Rounded off Allen bolt stuck!

[wookiee]

Hi

Right well I have an allen bolt that has been rounded off so that an allen key will not grip. After looking online I tried tapping a larger torx socket into the bolt but that too would not grip. The bolt is a 5mm allen so I then tried a 6mm tapped in and it still wouldn't grip. The bolt is now completely mangled and is recessed so I can't get a grip on the head either! I have seen screw extractors has anyone had any experience of these? Any help of tips gratefully received.

Thanks in advance,

Doug

 

[ti_pin_man]

smaller metal drill into bolt area and steady slow drilling, this will probably collapse the allen bolt and you extract the pieces. The vibrations will also help loosen things as you go. Usually the bolt is replaceable but the thing its in isn't.

 

[wookiee]

smaller metal drill into bolt area and steady slow drilling, this will probably collapse the allen bolt and you extract the pieces. The vibrations will also help loosen things as you go. Usually the bolt is replaceable but the thing its in isn't.

Yes the "thing" in this case is an XTR crank arm!...bit worried that I might damage the thread on the arm using the drill method though :?

 

[greencat]

Re:

I had the very same problem yesterday while trying to get some rotors off some new secondhand wheels. Both rotors had one stuck bolt that the previous owner had kindly rounded.

Can you cut a slot for a screwdriver - and perhaps tap it round? Or use pliers on it (probably not from the sounds of it)? Weld or epoxy an allen key to it? Maybe some gentle heat or freezing might help?

In the end I managed to bend and rotate the both rotors a little which loosened the bolts enough that I could get the pliers on them.

 

[ti_pin_man]

Yes the "thing" in this case is an XTR crank arm!...bit worried that I might damage the thread on the arm using the drill method though

an even smaller metal drill , pilot hole might be the course of action, then work up in size.

 

[drystonepaul]

Re:

Where is the bolt Doug?

If the torx trick hasn't worked then I normally tackle rounded out bolts be drilling a 2mm hole as centrally as is possible into the head of the bolt. Drilling into the bolt shaft for a least 3mm past the height of the bolt head or cap. You need a high quality, sharp drill bit to do this successfully. Getting this bit right is critical to further steps.

The use progressively larger drill bits (3mm then 4mm then 5mm) to drill out to the depth of the bolt cap. With an M5 bolt, the 5mm drill bit will eventually shear off the head of the bolt leaving the threaded shaft in the frame/component.

You need to be careful not to drill too far and damage the frame/component.

Once the bolt head is removed, then the pressure exerted on the bolt taps will also be significantly lessened.

At this point you will have your bolt shaft with a 2mm hole already drilled into it from stage one.
You can usually wedge in a torx bit and unscrew the bolt here.

If it's still stuck then continue drilling with a 2.5mm drill bit. This will normally get the bolt moving as well. You can back the drill out with the bolt shaft.

It's sometimes necessary to keep drilling the bolt out completely and then re-tap the hole.

 

[drystonepaul]

Re:

Ah. Just seen subsequent posts made whilst typing my method.

Same method with a crank bolt. You may need a center punch to mark the bolt for drilling. Again though, start small (perhaps 4mm drill bit for crank bolts) and work up to an 8mm bit.

Once the crank is off, the remainder of the crank bolt will probably wind out by hand.

 

[saladodger]

As per greencat above I had the same problem and simply tapped a "slot" on either side of the recessed edge and used a flat screwdriver to undo. Not always possible I guess but worth a try and doable without any special kit. If not ditto the other suggestions. Good luck

 

[wookiee]

Re: Re:

I had the very same problem yesterday while trying to get some rotors off some new secondhand wheels. Both rotors had one stuck bolt that the previous owner had kindly rounded.

Can you cut a slot for a screwdriver - and perhaps tap it round? Or use pliers on it (probably not from the sounds of it)? Weld or epoxy an allen key to it?

In the end I managed to bend and rotate the both rotors a little which loosened the bolts enough that I could get the pliers on them.

Hmm no the bolt is sunken flush with the arm so cant cut a slot and pliers no chance...looking at how mangled the head is I doubt epoxy would help either! See pic

 

[juice]

Yes the "thing" in this case is an XTR crank arm!...bit worried that I might damage the thread on the arm using the drill method though :?

I once tried drilling out one of the adjuster screws on a front mech. The good news is the screw is gone. The bad news is..you can guess it...the thread is completely gone as well.

Today i would choose another method to destroy my bike parts. Maybe i would cut a slot in the bolt for a screwdriver and try securing the screwdriver with tin-solder.

I guess the result could be similiar in the end but if you really try this we could at least say for sure that this won't work either. :facepalm: