Help!
I have a really nice Miche seatclamp on my bike but unfortunately the Allen Bolts appear to be made from playdoh…

…does anyone have experience of removing one that is (countersunk) and more or less fully rounded out now?

You could try hammering in a torx bit

What he said.

Hot & Cold helps – kettle full of water, freeze spray, penetrating oil. The hammering in of a torx key will probably shock it loose though.

as above
can you punch it round, ie get a very sharp punch (or screwdiver or chisel etc as a lot of other people call it), then make a 'dot/indent' on the edge of the bolt by hammering the punch straight down, then angle punch in indent so that when you hammer it's driving in the undo direction,
(*also seen people using an impact driver and battering it but thta was motorbikes with a fair bit more metal)
if that fails then google on easyout

An electric screwdriver set to a low torque will often move stuff that's stuck too. On big nuts and bolts, an air impact gun works wonders but it might be overkill on a bike 😆

Molegrips are pretty good at doing this if the head isnt resessed, & you can get to it with em.

Drill the head off with drill bit the same size as the thread of the bolt.

oh god, put the tools down, araldite is your friend

Bolt extractor kit? There are quite a few on eBay at what to me is a reasonable price. Not sure about an impact driver. As above may not be enough metal, though I have removed small bolts with one. Th eproblem I think you will have is resisting the force of the hammer blows. I can see it just driving the collar round the seat tube rather than acting to free the bolt.

Thin pilot drill, then wider drill bit through the bolt.
Did this to a stem cap bolt last week.
J.

I drilled out a Ti bolt stuck in a thomson stem the other day using a cobalt drill. took hours but did the job in the end. method as above, pilot drill then bigger drill. sometimes the drill virbation will loosen the bolt up and it will just spin out.

The tool designed for the job – easy outs.

http://www.google.co.uk/m/products?source=mog&hl=en&gl=uk&client=safari&q=easy%20out

Hacksaw, or dremel & thin cutting disc, through the bolt where it's exposed by the slot in the clamp.
As long as the bolt head rounded because it had been overtightened,not because it is seized in the thread, you should be able to get the stub out.

Great.
I have put the powerdriver on for a quick charge and will see which method works. I'm a bit baffled by the reference to the Araldite though?

Thanks.

The tool designed for the job – easy outs.

And almost universally regarded as the absolute last resort, because they're made of hard, and therefore brittle steel. And they break. And then you can't drill them out.

Irwin Bolt Grippers are also designed for the job, and won't cause that kind of uglyness. But they also don't work for recessed bolts.

MTG – the saw worked, although nearly shot myself in the bollo#$ !!

Thanks

Easyout extractor. I use them everyday at work. great tools, just make sure you use new drill bits.

I'm a bit baffled by the reference to the Araldite though?

I'm guessing he means to glue something into the bolt head with Araldite that then allows you to get decent purchase on it?