Removing allen screw from seat post

[Rebel Ian]

I've somehow managed to overtighten the allen bolt that holds the seat post and in the course of doing so have buggered the bolt. An allen key now just turns in the head of the bolt rather than actually turning the bolt itself.

I need to get the existing bolt out - any clues?! Secondly, I need a replacement allen bolt. Do any LBS sell these?

 

[machew]

You can get a set of drill bits that will drill screws out if you have rounded of the top. You may be able to get one small enough for the Allen screw. Failing that there are some Allen keys that grip on the flat bits and not on the corners (snap-on i think does this)

 

[Gareth]

Any LBS should be able to supply you with a replacement socket head screw (Allen).



I have been extracting damaged and sheared bolts for well over 30 years now, and so rely upon my very expensive Snap-On/ Bluepoint set for anything over 6mm diameter, but for screws and bolts less than 6mm you cannot beat this "Pro-grab-it" set made by trend: http://www.machinemart.co.uk/shop/p...t-damaged-bolt-screw-remove?da=1&TC=SRC-screw extrator

They are designed predominantly for removing damaged countersunk wood screws, but I have often used my set for small diameter bolts without a problem.

They might seem a little pricey, but when you need them they are worth every penny: Lois and I recently moved to a 70 year old house and without this extractor set, removing and replacing doors and hinges would have been an awful lot harder.

 

[PpPete]

Before you get busy with the drill - if you have a cheapo set of Torx screwdriver bits. Find the size of bit that won't quite go in the rounded-off hole. Now hammer the little sucker in. 1/4" hex to 1/4" square drive adapter and 1/4" ratchet (or even mole wrench on the projecting flats of the bit) usually gives enough "bite" to get it turning again.

LBS used to be good for things like replacement allen bolts... but, along with everything else "We can order one in for you - book the bike in so we can check the size needed, be about 3 weeks time before we can look at it "

I did however, come across this the other day.

 

[twobiker]

Sometimes a flat head screwdriver will fit across the angles and turn it.

 

[02GF74]

.... and if you havre a drremel, you cut cut a slot in the head and use flat bladed screwdriver.

the bolt is noting special, any decent fastener supplier should have it in stock, in different grades , you want mimimum of 8.8 but you can get 12.8 for not much more, or stainless (so no rust, about same strength as 8.8 I have not had one snap yet).

 

[Rebel Ian]

Thanks all. I'll try a few of the suggestions made otherwise it's off to the LBS to outsource my problem!

 

[peelywally]

if the nut sits proud and you can pinch it inbetween two fingers then your ok

get a pair of vice grips and grab the thing as tight as you can and loosen it that way you shouldnt need much purchase if you can grip it tight enough ,

if its sunken lbs might be your best bet but ideas above will work , bit of wd 40 loosens it btw just spray a small amount on and angle bike so it works into threads , you might try heat via blowtorch to expand threads but i would only recomend this on old steel it will ruin alu or any paint job and dont even consider it on carbon

spare allen bolts are ten a penny lbs would probably give you one or grab one off a dumped broken bike i dont think theres a spec issue relating to weight or quality with allen bolts

 

[mattsccm]

Bike shops will try the above techniques before moving on to a stud extrcator if they have one.