The NDS bb cup is cross-threaded and the crank-pulling threads are all stripped. I tried my best to use the crank puller like a tap and clean the threads as I went in perfectly square (spun cranks and made sure tool stayed center). How does one get crank arm off?
by misterericman
7 Comments
To prevent this next time, hand thread it in as far as possible, then use a wrench to turn it as far as it will go before removing it.
The most reliable way to get it now is a ball joint separator “pickle fork” and a mallet. This has the possibility of damaging your bottom bracket, and you don’t want to reuse the crank arm as well.
You can use some sort of external puller – or because the crank is ruined now anyway carefully ride around with it like that and it should fall off.
One of these will do the job.
https://www.harborfreight.com/8-in-3-jaw-gear-puller-63952.html?utm_source=google&utm_medium=cpc&utm_campaign=21901271210&campaignid=21901271210&utm_content=171677806502&adsetid=171677806502&product=63952&store=3342&gad_source=1&gbraid=0AAAAADAHb4dmdbvMlYKm2AIU15oQygVCg&gclid=CjwKCAiA5eC9BhAuEiwA3CKwQrJfupHe_NIcQT6YU4UINXIbo0i3r3zcgyB6vrvyONDvtQmdRLB1gBoCktgQAvD_BwE
Oops. I did the same once. Luckily I was trying to replace the bb so didn’t care about messing it up. A torch (or other heat) and a hammer will get that off pretty quickly.
I’d stick a crank bolt almost all the way home, like wound out a coupla mm, then whack it with hammer while pulling on the crank. You might have to wind the bolt out and whack again… maybe even a few times, but eventually it’ll pop off. If that doesn’t work, cook the crank around the drive with a blowtorch to expand it around the taper, then whack the bolt. Failing that, I’d cut a slot in the back of the crank drive with a cutting disc on an angle grinder and just pull it off – it’s scrap anyway.
Unior has a crank puller for damaged threads. It basically cuts itself into the crank arm: https://www.youtube.com/watch?v=ySewKpuHJu0
Var has a kit for that: it contains a tap of a higher diameter to make new threads and a matching diameter extractor => [https://www.vartools.com/kit-reparation-du-taraudage-d-extraction-manivelle-m24x150-c2x36004241](https://www.vartools.com/kit-reparation-du-taraudage-d-extraction-manivelle-m24x150-c2x36004241) (site in French, because French brand, I don’t know if they ship where you are).
I used it in a similar situation, really a life saver.