I've just been through my shed looking for bits to build up a bike for my missus and found a working rear brake and a front brake in which the pad retaining bolt is rounded out.

I'm sure that 'drilling it out' will come up but as far as i'm concerned you might as well ask me to build a suspension bridge; are there any other options?
Cheers.

Not quite sure what bolt you mean but hacksaw/Dremel a slot across the head and a flat bladed screwdriver.

you wont be able to drill it out as the bolt is steel and the calliper is aluminium alloy – you'l just gash up the calliper.

Is it a hex bolt?

Try and tap a torx bit into it to see if you can get some purchase.

Try and cut a slot – deep and wide enough – for a screwdriver to try and get it out.

Molegrips on the head?

Bit of penetrating fluid first to make it easier?

then replace it with a bent paperclip or splt pin.

ive got one in a louise caliper.
hammer in a torx head is first on my list
dont think a small easyout will work as the hex head is not deep enough
i might be able to get a purchase on the middle of the pin, but i doubt it

heat and penetrating oil as a last resort

Is it a hex bolt?

Well, it was, now it's a 'circle bolt'.

Hmm, might try the hacksaw/flat head route first but failing that some other good ideas. The Torx bit also sounds a goer if I can't work the hacksaw blade in there (no dremel – how i realise i should have one now!)

Molgrips were my first attempt but there's not really enough room for the fat ended ones I have.

Cheers folks 🙂

Avids??

Torx key hammered in works a treat. Know a few people (including me) who have done it and are still using the bol with the torx key!! Avid COde's for me.

Avids??

Old deores but I've got Avids on my bike so it's useful to know about the torx trick 🙂

I had to do this on a set of Deore 555s a couple of weeks ago.

Torx bit failed, so I cut a slot in the bolt and it worked. I did manage to bend a Leatherman screwdriver attempting to remove it, but strangely my Ikea fiver tool kit worked on it.

if teh pin extends out the other side like it does on minis i flattened the other end with some plyers and unscrewed it by clamping on teh flattened end with an adjustable

Torx – fail.
Slot cut – fail.

WD40 penetrating hypothesised rust.

Round two….?

build a suspension bridge.

Why didn't either of those work?

might take a while but is epoxying in an old allen key or anything else that you can grip worth a try? Is any gluing stuff strong enough?

I've got the same problem with some Magura Louises. I'm going to try an impact wrench with a torx bit first, if that fails then I might try gluing in a hex bit but more likely bribe a friend to get it drilled out on his lathe. Very annoying it is too.

Why didn't either of those work?

Torx: no vice so i couldn't get the brake still enough to get an accurate shot at it – more no facility than fail

Cut slot: the bolt looks semi-corroded in so I'm trying to do something about that…

Sounds slightly ridiculous (and probably is), but needle-nosed pliers on the main shaft of the pin with molgrips clamping them shut proved the only way to get the stuck pin out of Maguras.

Slots/filing flats for spanners/stud extractors all failed (well, I failed to make them work…)

Knackered the pliers, but saved the brake.

Never brake ever again. That way you'll not only get faster, you'll save money on pads too. In fact, if you're not going to brake you could just forget the brake altogether and save weight! You're welcome.

On a more serious note, is the caliper a one piece? If not, would separating the halves help?

I had exactly this problem. Completely fixed by using a gadget whose name I completely forget, but anyway, you put it in your drill, and then stick it in the scooped out pin on your brake and drill away. The gadget is like a screw with a reverse thread and it basically bites into the retaining pin and then pulls it out, like as if it has magical powers.

Edit – just looked in my toolkit. The device in question is called a "damaged screw and bolt remover", made by GRABIT. I tried all the options mentioned here and none worked – then GRABIT changed my life.