Sheared bolt issue - advice sought

[borisface]

Hi everyone,

I was cleaning (its a fairly rare occurrence) my fixed wheel bike the other day and needed to take the rear wheel out. To do this I had to unscrew the bolt that fixes the mudguard stay to the frame. Unfortunately, the bolt simply sheared in half leaving most of the bolt screwed into the frame. I've put a P clip on the seat stay and fastened the mudguard stay to that as a temporary measure. However, I would like, if possible to remove the snapped bolt and use the mudguard eyelets as this gives a more secure fitting. The frame is aluminium and the threaded hole for the mudguards is in the seat stay rather than a looped eyelet on the rear dropout. What would be my best option in removing the bolt?

[cyclop]

Try grinding bolt flush with frame then drill out with a 2 or 2.5mm drill.Apply lube spray and some heat then attempt to remove remaining stud with,say,one jaw of some long nose pliers pushed into the hole.If this fails, use a 5mm drill on the remainder.This will ruin the threads so an M5 nut and bolt could then be used to secure the guard.Hope I haven,t offended any engineers out there but this is what I would do.

[gregoryoftours]

If there's anything left of the bolt poking out of the frame I'd try soaking in penetrating fluid and then heating the bolt with a blob of solder and a soldering iron and cooling it down a few times before trying to to get it out with a pair of mole grip pliers. Failing that I'd try the grind flat and drill method, although it might be hard to do well.

[531colin]

Google "left hand drill bits"......yes, I know it isn't 1st April......also "easy out"....although they are anything but easy, and mostly too big.....

If you can't for example, saw a slot in the snapped bolt and use a screwdriver, or grip it with mole grips, the best bet is to drill it with a left hand bit, then the drilling torque and heat might possibly get the thing out. File the end flat and centre punch to start the drill....
Steel bolts in alloy produce white stuff, which is some sort of oxide, I think. Warm it up as much as you dare (hair dryer?) to drive the wet out, put oil on it while still hot and it might be drawn in as it cools.......drying the oxide shrinks it from crystalline to powder, and helps loosen it a bit.

Good luck

[cycleruk]

I don't know if it makes any difference but I presume that it has a riveted thread insert in the seatstay?
In the end it may be possible to get a new insert fitted if nothing else works.
As above, I would start with a small drill and gradually increase drill size until you are able to get something into the bolt to hopefully undo it. I have had results using a file tang inserted into the bolt hole to unscrew it.
Another option:- Usually the drilled hole is slightly off-centre, and using an appropriate drill size, it will just skim one side of the insert threads. This leaves the rest of the bolt thread loose enough to be dug out.

[Brucey]

If it were my bike (and it wasn't a black-finished 12.9 caphead screw that had sheared off) I'd weld onto the end of the bolt/stud using MIG welding. This gives you something that gives purchase on the bolt and the heat is x10 more than you will get with a soldering iron, so may help the thing come free.

That is 'the best method of removal' IMHO because the chances of drilling a steel bolt out of an aluminium insert whilst leaving usable threads in the insert is.... slight.

Worst case is the you remove the top of the bolt and the top of the insert, that lot disappears inside the seat stay, and you fit a new insert (aka nutsert, rivnut) into the seat stay.

Bolting the stable door after the horse has gone, this, (of course) but it is always a good idea to remove these bolts once a year and to refit them with a load of copper-ease or similar anti-seize compound.

cheers