drilling out a seat pin bolt?

D

daysnways

Dirt Disciple
I have acquired a late 70's/early 80s frame with a recessed allen key bolt seat pin.

I can't seem to get an allen key to fit it, I have a few, either just too big or just too small. The bolt is a little rounded off.

Go out and get a complete set of allen keys, or drill out the bolt?

Will drilling it out guarantee to free it though.

The frame has evidently been left outside or in a crap garage for some time and the bolt is very rusty. I suspect that the seatpost may well be stuck.

The other side of the bolt protrudes only around 1mm...

It requires a respray, so it needs to come out. Any suggestions?
 
Spray some penetrating fluid onto it and leave it a day or two before attempting another go, as it is suffering from corrosion bonding. The right size key is a good start but only if the profile is still good on the bolt. Drilling it out works ok if using a lefthand drill bit and being careful as it could easily just start to spin around, also using a local heat source to try and break the corrosion bonding can help but try not to overheat it, one of those electric paint strippers is a good option for this.
 
Re:

penetrating fluid, leave to soak, then tap a tight-fitting torx bit in and undo.
You will need a new bolt though
 
both of the above. torx bit has worked for me and a lot safer that drilling.
I also have a set of reverse threaded bolt extractors, worked a treat too on allen heads
 
Agreed on the Torx trick. It worked well for me with a heavily-corroded BB eccentric on my tandem. If you taper the ends of the Torx a tiny bit with a file it helps it fit into the recess easier rather than tipping over.

One other thing to try is to see if imperial Allen sizes will fit. A set of imperial keys is usually only £3 or so.
 
Re:

thanks folks, worth getting an imperial set of allenkeys?

ahh missed above post, cheers, going to try that route.
 
Assuming there is a slight gap left between the two lugs clamping he seat post, is there any way you can use cut down hacksaw blade or any thin grinder in there ? once the its cut then you are able to prize them apart.

Agreed with above once recessed Allen bolts loose their shape real problem: as you may know one half screws into the other half, Allen bolts are made of hardened steel, but if you can get a good centre punch mark on one side maybe with a good drill bit, you could maybe drill one side out.
 
Assuming there is a slight gap left between the two lugs clamping he seat post, is there any way you can use cut down hacksaw blade or any thin grinder in there ? once the its cut then you are able to prize them apart.

Agreed with above once recessed Allen bolts loose their shape real problem: as you may know one half screws into the other half, Allen bolts are made of hardened steel, but if you can get a good centre punch mark on one side maybe with a good drill bit, you could maybe drill one side out.
 
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