Rounded Bolt in cranks.

anyone got any tips? need to take this off to change the BB.

1 Attachment

Your not strong enough...how did that happened

Er, drill, tap, undo, might be the only way?

Is it part way out? Mole grips?

ask the last owner bf me...no fuckin clue man

I would try a chisel or drill the head off

http://www.screwfix.com/p/laser-torx-extractor-bit-set-7pcs/6329F?kpid=6329F&gclid=CjwKCAjwrO_MBRBxEiwAYJnDLDicLKHYQDNC84ky1BVtWS4qZMATX3yh4zrk1ZIGQK6xJBkd60QyLhoCnTYQAvD_BwE&gclsrc=aw.ds&dclid=CNT-1vbI69UCFUWMUQod72kHOg
might work
or if you can drill into the centre of it
http://www.screwfix.com/p/screw-extractor-5-piece-set/18643

Exactly that. The least destructive way by far :-)

Do you have a torx bit big enough? Bash it in until it bites and use that?

That's grim ...

Drill out middle to detach head of bolt.

Remove crank.

File flat surfaces on what's left for spanner.

ive seen this before but every shop i asked about how can it be done no one said anything bout these...

I've linked to two diff types, the second link is traditional type of screw extractor and you'd need to be able to drill into the centre(ish) of the bolt and secure the spindle on the other side of the BB to use it but this is standard approach to damaged bolt/screw heads.
The first link is a Torx extractor, it "might" work if it can get enough bite and it's big enough to fill the gap.
Otherwise drill the bolt head and heat the BB spindle and you might be able to extract leftover bolt stub. If you know somebody with a mig welder they could weld onto the bolt stub.

Sorry all engineering /metalwork type approaches from me.

BLB crank.

Just use an angle grinder.

Yeah this too.
:D

Bring to your lbs and theyll sort it out for you much better that tempting with no idea how to do;)

this is just knowledge

Just like tattooing bro diy

If you have a dremel or other rotary cutting tool, you could use a small metal cutting disc and cut a a slot across the bolt, then use a wide edged tool to unscrew the bolt. Alternatively if you could find a large flat screwdriver with a head as wide as the widest points across the bolt hole you could jam it in and unsrew the bolt that way. Definitely both bodges, but the latter would be easy to try before investing in bolt extractors etc.

If you have a dremmel cut two flats on the outside and use a spanner or adjustable to turn it

I wouldn't bother with those Screwfix screw extractors. They're shit. All that will happen is that the screw extractor will break when you try to turn it, and then you'll be in exactly the same position as you were before, except that in order to drill the bolt out you now have to first drill out a hardened tool steel screw extractor as well. Been there, done that. If the bottom bracket's dead and needs changing, just drill the bolt out. It'll trash the threads on the BB, but if it's dead anyway then that's no loss. Start with a 4mm or 5mm drill, then take it up gradually to 8mm. If you've got the hole centred, the bolt should then come off nice and easy. If not, take it up to 10mm and Bob will definitely be your uncle.

well, a tattoo is for a life :(

thanx for the tips guys, really appreciate it

This has been on Facebook a few times. Could it be extended to be able to remove the Allen bolt?
https://youtu.be/MaCYyL4UJAA

Unlikely. The torque required to undo a crank bolt is going to be much greater than the force required to undo a screw screwed into a piece of wood. In the past I've tried gluing torx bits into rounded allen key bolts with steel-reinforced epoxy, and then trying to undo them. It's worked a few times, but mostly it doesn't.

If you can get the non drive side bb cup undone and then get enough room behind the crank on the drive side to get the cup out then take it all apart so you just have the crank and axle. Find a firm with a spark eroder and they will have the damaged bolt out fairly quickly and the threads / taper will not be damaged. Alternativly a peice of metal welded on to the bolt head may be another way. Easy outs etc are generally a total waste of time.