Sheared seatpost pinch bolt

So, I sheared my seatpost bolt. Wanker. Anyway, after much swearing, and some slight unwitting obliteration of the paint around my seat tube cluster, I managed to file the other ends of the bolt flat enough that I could get the other end out with a spanner. Phew.

My issue is what to put back in there.

The current bolt looks like this

https://www.dropbox.com/s/evb3sowqr26biu0/Photo%2016-08-2012%2011%2027%2000.jpg

Allen head, 5mm diameter.

Problem is, no combination of seemingly appropriate search terms cough up what I'm looking for. What I really want, is to be able to fit a campagnolo style two part bolt, alas it's not gonna go; my brazeons look like this:

https://www.dropbox.com/s/gzlzswruo2eltlg/Photo%2016-08-2012%2011%2054%2058.jpg
https://www.dropbox.com/s/cw06yrhfzs38kh9/Photo%2016-08-2012%2011%2054%2040.jpg

with the head on the bolt entering the recessed side, and this providing the brace, presumably against which the seat tube is pinched shut. This strikes me as a fairly rough way of doing things, but someone with far more knowledge than me will hopefully tell me why I'm wrong.

In typing this, I've realised I'm probably being obtuse, and I just want any m5 bolt of the right length, but as with all small parts, it's a pain to order them only for them to be the wrong thing, so hopefully someone can confirm my suspicions?

Is your seatpost too small for the frame? It looks like the bits the bolt threads through have bent inwards as they've tightened further than intended. The bend they then imposed on the bolt is probably what caused it to shear. (It is just an ordinary stainless steel M5 socket head screw.)

Maybe you could drill out both sides as they are to take a 2-piece bolt, but that would be hard to do well without a drill press, and wouldn't leave you with much metal.

I'd probably try bending them outwards until they lined up again, then see if a larger diameter seatpost is needed. You can slip a penny between the two sides then screw a bolt into the threaded side from the outside to force them apart, and push sideways on the bolt to bend that side alone.

Plenty of fairly nice frames use the system on your bike, there's nothing wrong with it and certainly not worth taking a drill to it. It's going to be practically impossible to drill the hole straight even with a press, since there's no convenient way to hold the frame perfectly horizontal on a press. You also risk damaging the seat tube if you veer too close to it.

As moth said it's just an ordinary 5mm screw with an socket head, no need to "order" it from anywhere, you should be able to find it in most hardware shops or ironmongers. just measure the breadth of the entire seat tube brazeon to get the right length. But do check that you have the right seatpost size.

I did have a go at straightening them myself, and had indeed puzzled over seatpost size, but I shouldn't need bigger than a 27.2mm seatpost in Reynolds 653 though right? Might just make a small shim anyway for the sake of keeping everything straight and tight.

Thanks for your hep, both.

I agree with Shanghaied. Plus, the Campy-style 2-piece has a sort of indexing key, or nub, on at least one of the pieces if not both (this it to keep it from rotating in the hole as it is tightened). You would have to grind or file the nub(s) off of one or both pieces as applicable, thereby allowing the pieces to rotate freely -- which is okay if you have two of the same sized Allen spanners to use, one on each side, simultaneously. But still...
If you are fortunate enough to have a piece of drill rod (high carbon steel) that is the same diameter as the unthreaded portion, you could insert that (or the shank end of an old drill bit that you don't care too much about) into the unthreaded side and use it to bend...er, carefully "form" at least that side back apart. As to the other side -- it looks as if it may be a bit stripped, too? -- you might want to have that retapped. Most good bicycle shops should be able to do that for you, maybe even for free if you buy a jersey or something. ;-)