Recutting thread on stripped cranks

I've tried a few ways of easing a stripped crank off, but no joy yet. Just got hold of a Cyclus crank repair toolkit. It's got a reamer and cutter for a 24mm thread, plus a 24mm crank extractor. It's also got a handy centring guide for the cutter. Hopefully I'll have some success and be able to carry on using the S75 crank!

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Square taper and/or bust!

I managed this once with gear/bearing puller. Bought a cheap set of three from screwfix... Cheap indeed as it didn't really fit around the 5 arms. After some manouvering and a bleeding lip (don't ask), the cranks came off.

Square taper often busts!

I tried a dreaded three-arm gear puller once. Didn't work with that one, unfortunately. The puller broke. Not ideal on a five-arm spider.

With this current crank I had tried liberal amounts of heat (to make use of aluminium's greater thermal expansion coefficient) and riding a good few km without a crank belt. No loosening joy was had.

I'm really happy about finding a tool with a centring guide - should be so much easier to cut the new thread properly and save the crank. I'm going to get a handy engineering friend to help.

It was a right faff and I would recommend something more robust or with more arms, or having the claws against e.g. a piece of wood and not the crank arms directly. In my case, it was an old Shimano crankset that I was willing to sacrifice, and that's what happened in the end.

Here we go, reaming away the ruined threads. Nervous times.

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Juicy new 24mm threads now cut

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Crank finally off! Now I can keep that S75 crank as long as I have the 24mm extractor handy. Happy days.

Shame the cutting toolset is stupid-expensive new.

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Wow! Looks like you did a great job.

Yeah, it's expensive and when I inquired in the past, not many shops were willing to go through this faff.

Interesting to see this, glad it was successful!

Well done, that's a neat job. I stripped the threads on some crappy FSA cranks that I wanted off, used a bearing puller to get them but that's much less ropey

Thanks chaps. It took less than 15 mins, and I was going slowly slowly. This crank is now earmarked for an NJS build.

That's very satisfying to read, thanks for sharing

Maybe use a lube when cutting the threads

I used cutting oil liberally. Wasn't going to compromise with that crank and those expensive tools.

Looks like you did a good job. A point regarding the thermal expansion coefficient of aluminium though. My understanding is that if you heat up the cranks, they will expand in all directions, i.e against the axle as well, making them harder to remove. So that would not help in removing alu cranks from a steel axle.

Good point. I figured that expanding in all directions would end up making the taper marginally wider overall. But no joy. Still, the Cyclus toolset saved the day.

Not to be rude, you would amazed that people don't.

Good on you for doing things correctly.

Sorry to interject, part of the purpose of heating is to get the expansion and contraction of the materials to 'break' the bond between the two materials.

That is why cooling steel frames with alloy stuck seat posts works, as the Alloy contracts more than the steel frame hence breaking the bond.