Removing a stripped crank?

[Big John]

We've had this a few times at work and it's not scientific and it's not pretty. Beat the living daylights out of the crank with a lump hammer and make sure the workshop is empty apart from yourself because when it comes off it'll kill someone. We had one shoot out of the fire door, which was open at the time (it was a hot summer's day), and on another occasion I was the recipient of a rocket propelled crank arm in the shin. I think I might still have the lump to prove it. On another occasion the boss took an angle grinder to the crank arm and it took an age. I've actually got a three arm bearing puller, not that I've ever been a car mechanic (it was my dad's), and I thought that might work but there wasn't enough room to get the arms of the puller to grip it. If you do resort to an angle grinder make sure the sparks can't reach anything flammable

 

[raleighnut]

By all means use a chisel if scrapping the arm but I use a brass 'drift' on one of my bikes that I want to fit the crank back onto.

 

[palinurus]

I've actually got a three arm bearing puller, not that I've ever been a car mechanic (it was my dad's), and I thought that might work but there wasn't enough room to get the arms of the puller to grip it.

The dimensions of the puller and shape of the 'feet' are important, plus ideally need one that's going to work both on the drive and non-drive side.

 

[silva]

The one and only time I had to get off a crank I just took a handsaw, it's just easy aluminium. I started from 2 points and when most cut, I took a chisel and split the remainder.

 

[Cycleops]

The one and only time I had to get off a crank I just took a handsaw, it's just easy aluminium. I started from 2 points and when most cut, I took a chisel and split the remainder.

A lot of work when it will just remove with a few sharp hammer bangs.

 

[Gunk]

I’ve just posted on the “fettled” post. I’ve had success using a modified bearing puller

 

[Gunk]

A lot of work when it will just remove with a few sharp hammer bangs.

They don’t always pop off

 

[Gunk]

The dimensions of the puller and shape of the 'feet' are important, plus ideally need one that's going to work both on the drive and non-drive side.

I had to grind down the feet to fit behind the crank.

 

[silva]

A lot of work when it will just remove with a few sharp hammer bangs.

Well no, it was a 5 min job, and I ticked the chisel in the remaining alu, not bangs / blows, in order to not damage bearings / whatever.
That't the benefit of a saw: no collateral damage.

 

[Chris S]

If the stripped thread is on the non-drive side then remove the drive side crank as normal. Then unscrew the adjustable cup to gain access to the bearings, etc. If you want to replace them you will have to break the cage and use free bearings.

 

[classic33]

Another for a gear puller.
Maybe a two-armed rather than a three.

 

[FrankCrank]

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.

I've not had occasion to try this method personally, as stated. I have heard it suggested though on several occasions. Pretty sure RJ the Bikeguy thought it worth a try in one of his vids. If I was in a situation as the OP is, I'd certainly try it out, costs nothing other than a little curiosity.

 

[Emanresu]

View: https://www.youtube.com/watch?v=jrpIoXxVyTs

 

[Punkawallah]

Wot ‘e said.