Removing a stripped crank?

[Andy in Germany]

Any suggestions how we could remove a crank from a square taper BB when the thread in the crank is stripped bare?

WE need to get the BB off, and unfortunately this now seems impossible; normally we wouldn't mind but it's an otherwise perfectly good gents town bike.

 

[fossyant]

Cut the crank down to the axel. Job for a Dremel.

 

[Dogtrousers]

I'm sure I've seen pictures of automotive bearing puller tools being used/suggested for this. Unlike a regular crank extractor which grips the crank using the thread (which is stripped) and then a central screw that pushes the axle, these have arms that reach around the back of the crank and hold on there, and the central screw that pushes on the axle. Does that make sense?

I don't know anything about automotive tools.

Edit: If you google "bearing puller stripped crank" you will see what I mean. I don't know anything about this, I've never used or even seen a bearing puller. I've just come across mentions on the internet.

 

[DCLane]

Either a puller, as @Dogtrousers suggests above, or a lump hammer/sledge hammer and chisel to force the crank off if you're less sophisticated.

 

[Jameshow]

Angle grinder / hacksaw and guess the angle of the taper!

 

[Cycleops]

Angle grinder? My local bike mender had never seen a crank remover until I gave him one and still doesn’t use now. A lump hammer and a cold chisel is all you need. Works every time, guaranteed. In fact I did one last week on a BSO that had spoiled thread.
Take the bike off the tyres as they will absorb the energy.

 

[Andy in Germany]

Angle grinder? My local bike mender had never seen a crank remover until I gave him one and still doesn’t use now. A lump hammer and a cold chisel is all you need. Works every time, guaranteed. In fact I did one last week on a BSO that had spoiled thread.
Take the bike off the tyres as they will absorb the energy.

What's a 'cold' chisel? I'm guessing something fairly thick. I'm also guessing you hit vertically and then try to lever against the remains of the BB, is that right?

 

[presta]

What's a 'cold' chisel?

Chisels for cutting (cold) metal.

 

[richardfm]

hammer a ball joint splitter in the gap between the crank and the bottom bracket

 

[palinurus]

Bearing puller / three-leg puller. I've heard of people using a wiper blade puller tool also.

 

[Dogtrousers]

Chisels for cutting (cold) metal.

I've never actually wondered where the name came from. But I'm very happy to know.

 

[FrankCrank]

Heard that just riding it with the crank bolts removed is enough to loosen. Not tried it myself.

 

[presta]

hammer a ball joint splitter in the gap between the crank and the bottom bracket
View attachment 709331

That's putting a heavy shock load on the bearings, which he might want to keep. If it's on the left it might also smash the BB cup if it's plastic, and create a whole new problem.

 

[fossyant]

TNT would do the trick just as well as some of these 'methods'.

I'd personally cut it off - done it before with a hacksaw, but for speed a dremel and a cutting disk. The crank will come off once you cut through the alloy - depends upon how much potential damage you want to do to the bike smacking it off.

 

[Ajax Bay]

Heard that just riding it with the crank bolts removed is enough to loosen. Not tried it myself.

Did you hear from someone who achieved this: i.e. had "tried it themselves"?
If so it's likely that the cranks were already loose (ie could be pulled off by hand before any riding).
The mechanics of the square taper interface mean that, with use, the cranks 'squirm' up the cranks (i.e. further than just by tightening the crank bolts tight) till they can't any more. I have "tried this myself" and have "heard" it is true, but have evidence to back this up.