Stripped Square Taper Crank Extraction Threads

Has anyone found a way to “repair” the extraction threads in a Square Taper type Crank?

I have managed to remove a Crank with stripped threads from a bike by bolting a drift onto the exposed Non-Drive Side Bottom Bracket cartridge. I then managed to pull the Crank from the Bottom Bracket taper by using a blow torch on the Crank, and freezer spray on the axle, while utilising the very last of the knackered threads that were still hanging on in there.

It seems a shame to chuck the Crank away, so does anyone know of a solution?

The tapers are fine, so I can easily fit the crank again, but when it’s time to change an inner Chain Ring, or the Bottom Bracket, I will be stuck with an even more challenging removing performance than this time.

Pip.

I think there is a solution, of rethreading and using a slightly larger extractor, I remember using a stronglight or ta extractor, if my memory serves me. however this is not an easy off the shelf job for parts.

Other option is helicoil it.

I'll check in the workshop tomorrow as I think there is a tool for it.

Helicoil? I guess you'd be limited to self extracting bolts after...

legrandefromage":iny6mehm said:

Helicoil? I guess you'd be limited to self extracting bolts after...

Click to expand...

Yeah cheers - I did take the Crank to my LBS this week, and was told that Helicoil was an option. I was surprised that I hadn't heard of this before (being 57 years old), as I had assumed that it would be too shallow. I was also surprised that the bike shop in question would be equipped with engineering tool shop type gear.

Anyway, the guy that I spoke to who booked the job in seemed quite positive with regards to getting a Helicoil in there. Sadly when I spoke to the guy today who was going to do the job, he gave me the impression that it was only possible to Helicoil the pedal thread, but not the shallow blind Extractor thread. He handed me my Crank back - perhaps a bit of communication breakdown between staff members?

LGF, you have however given me an idea. I may be able to "set" a Self-Extracting assembly into what is left of the Crank's thread. I'm currently thinking red Loctite, or even Araldite - Ooo, did I really say that :shock:

I don't really have any other very local bike shops to try, but it is interesting that a Helicoil was your immediate suggestion.

Pip.

You could always just use a different type up puller. Maybe a flywheel extractor for a motorbike, or some other 3 legged puller? That's what I use just when you pull the cranks off leave the bolt that holds it on in the thread a turn or 2 to stop puller damaging the threads on bb. Or get something to cover threads that you can protect BB threads with.
Good luck
Leigh

Re:

There is a tool out there somewhere, I can't remember who makes it, but it retreads the crank. I looked at it for mine, but it was something like £90 - several times what my cranks were worth. There's a you tube video of it too, I'll see if I can find it.

Re:

Here it is:
https://m.youtube.com/watch?v=2oizmWFx4PA

Re: Re:

XCDave":262ufapt said:

Here it is:
https://m.youtube.com/watch?v=2oizmWFx4PA

Click to expand...

Cheers - I'm not sure if the few bits of thread that I have left in my crank will hold this in place. Possibly worth a try if I can find the tool a bit cheaper.

Mobilecyclerepairs":262ufapt said:

I think there is a solution, of rethreading and using a slightly larger extractor, I remember using a stronglight or ta extractor, if my memory serves me. however this is not an easy off the shelf job for parts.

Other option is helicoil it.

I'll check in the workshop tomorrow as I think there is a tool for it.

Click to expand...

Thanks for looking. I think you may be referring to a 23mm Vintage T.A. crank puller - others including mine measure 22mm.

http://www.probikeshop.com/en/gb/var-cr ... 89473.html

I'll still need to find a way to tap out my Crank to the larger size.

Pip.

You'll struggle to find a M22x1 helicoil. If at all.

Re:

I've had the same issue. Easily resolved with a small clutch puller, a three armed tool that you should be able to find in and Halfords or B&Q, and you can pop the crank on and off to your heart's content, pulls on the central lump of the crank spider, pushes on the axle. Bob's your uncle.