How do you remove an Allen screw when the thread has gone...?

Fender76 · 14-11-2012 10:38PM #1

From a stem, the Allen key cant get any purchase cos the thread has worn away... Any ideas..?

Prenderb · 14-11-2012 10:41PM

Fender76 wrote: »

From a stem, the Allen key cant get any purchase cos the thread has worn away... Any ideas..?

Try stretching a rubber band over the head of the screw then using the allen key (with the rubber band still in place...). The rubber might get you a grip.

Presume that there's no "external" access to the fastener, i.e. you couldn't get a vice grips to it?

Mech1 · 14-11-2012 10:41PM

I assume you mean that the hexagon hole has rounded out?

14-11-2012 10:42PM

Plyers/vicegrip & WD40?

Recon · 14-11-2012 10:46PM

You can buy a bolt removal tool, which is basically a drill bit with a reverse screw on the end of it that drills into the damaged bolt/screw and screws it out. I've used them a few times and they worked everytime.

Fender76 · 14-11-2012 10:46PM

Mech1 wrote: »

I assume you mean that the hexagon hole has rounded out?

Exactly....

alphabeat · 14-11-2012 10:47PM

only way if the hex is worn is to drill it with gradually increarsing bit diameters until it falls away / collapses
then put a new one in.

or reverse drive the drill once drilled in

else bang a flathead screwdriver intothe hole with a hammer and try turning it .

either way the hex screw is toast

Rovi · 14-11-2012 10:51PM

The bolt with the rounded out Allen head is now effectively scrap, so you're looking to salvage things without damaging anything else at this stage.
A couple of options come to mind straight away:
Hammer in a slightly oversized Torx bit and see if that gives enough grip;
Drill off the head and remove the component, then extract the exposed stub with a Vise-Grips or similar tool.

Fender76 · 14-11-2012 10:51PM

alphabeat wrote: »

else bang a flathead screwdriver intothe hole with a hammer and try turning it

That solution sounds most promising...

GoodisonPark · 14-11-2012 10:51PM

Cut a slot across the head with a junior hacksaw and screw it out with a flat head screwdriver.

Hungrycol · 14-11-2012 10:52PM

alphabeat wrote: »

else bang a flathead screwdriver intothe hole with a hammer and try turning it .

Try this first.

I've rounded a stem bolt on my stem cos I forgot its only about 6n of torque and I have it 12n! So, so as I don't need to move the bars anytime soon I should be ok!!

Mech1 · 14-11-2012 10:52PM

if so, first put a lot of penatrating oil anyway you can around the bolt, even upturn the bike and check if there is a suitable hole to get oil to threaded part of bolt.

Then put a flat tipped punch or your allen key in the worn bolt head and give it a couple of sharp strikes of a hammer to help loosen bolt grip.

Find a Torx type bit that is just / only too large to fit in bolt head and hammer it into bolt head, it will cut your rounded allen key hole into a torx type hole. Do not remove hammered in torx bit before trying to turn it, bolt should loosen.

tippgod · 14-11-2012 10:54PM

alphabeat wrote: »

only way if the hex is worn is to drill it with gradually increarsing bit diameters until it falls away / collapses
then put a new one in.

or reverse drive the drill once drilled in

else bang a flathead screwdriver intothe hole with a hammer and try turning it .

either way the hex screw is toast

I second the flat head screwdriver. Have done it a few times and always worked. Don't worry about the star nut inside as they are cheap and easily replaced if it gets pushed down

kumate_champ07 · 15-11-2012 03:05AM

use a cheap allen key and some quick setting epoxy resin, leave till its finished hardening and then remove easilt

BlackBlade · 15-11-2012 03:41AM

some funny and desperate attempts there pmsl...
only solution to this is to get a torque or spline bit thats close in size and tap it in with a hammer then just screw it out as normal!
no other method other than the messy job of drilling will work!

RacoonQueen · 15-11-2012 06:51AM

Had a similar problem last night. Eventually found a pliers to nab it with.

Columbia · 15-11-2012 07:09AM

Chill the entire bike to -250 degrees celcius*, hopefully the bolt will contract more than its surroundings and simply slip out.

*you may need to adjust your gears after this.

You're welcome

Fender76 · 15-11-2012 07:37AM

Thanks everyone, gonna give the Hex bit a go, sounds the easiest..!

How do you remove an Allen screw when the thread has gone...?

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