NOOOOOOO, destroyed a chainset today

[Wibble]

Arsebiscuits and fiddlesticks.  Sorry for the swearing but *@%!

A friend phoned me up and was having trouble getting the chainset and bb off.  He'd already got the dust caps off, so I screwed the crank extractor in by hand, then got it snug with a spanner.  Then I stripped the sodding threads.  Bad enough when you do it to your own bike, but this wasn't even mine. 

I need reassurance here.  Was it my fault?  I thought I'd done everything correctly:

• The centre-y bit of the crank extractor was small enough to avoid the cranks and only touch the bb (I've got one that fails at this!)
• The centre-y bit of the crank extrator didn't sit proud of the outer bit, so the extractor could be screwed in all the way onto the crank threads
• Screwed the thing on by hand so I knew there were no crossed threads
• Made it snug (but not too snug) with a spanner
• Turn centre-y bit and wait for the thing to pop off.
• Swear as the blasted threads get stripped

What did I do wrong?  My friend is now going to have to take it to the LBS, who will do that patronising smile thingy they always do when someone comes in with a mess of their own making.  If only I'd not helped, then the bike shop would be the ones explaining why he needs a new chainset.

...or was it my fault?  I'm sure I did everything right, but was there something I'd missed or done incorrectly?  This is something I'm well practised at, and expected it to be easy rather than expensive for him and embarrasing for me.  Should it be both expensive and embarrasing for me?

For info, it was a square taper bottom bracket and had been on a very well used commuter for a couple of years.

[tiermat]

I wouldn't worry too much, I had the same thing happen to me, NDS came off no problem, when I turned it round to do the DS, the extractor went in fine, snugged up fine but when I turned the centre to pull the crank, it just removed the threads.  My thought was a combination of a well jammed crank and soft crank material lead to this situation.

I now have a frame with the chainrings and one crank stuck on it , thankfully it's not a bike a care too much about!

[Jurek]

The threads on ally cranks which accept the extractor are very fine, and prone to oxidisation (as is any untreated ally)

and had been on a very well used commuter for a couple of years.

Could this be the reason for you having stripped something of which there wasn't very much to start with?

[eck]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

[Domestique]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Thats what I was thinking 

The good news, a bit of leverage and a 'hot air gun' and you will soon have the chainset off 

[Chris N]

What crank extractor was it?  I've had terrible results with a Cyclo extractor but a Park extractor was much, much better - including being able to remove a crank whose threads I had previously knackered with the Cyclo POS.

[clarion]

That's the good thing about tapered axles - they're tapered

[chris]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Thats what I was thinking 

Could they be voices of experience?

[Domestique]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Thats what I was thinking 

Could they be voices of experience?

Yes 

[Wibble]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Already done when I got there.  

[andygates]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Thats what I was thinking 

Could they be voices of experience?

Add my experience to it.   

[Torslanda]

I'll get it off. Me and my friend, Mr 4lb Hammer.

And it will be usable afterwards.

J

[BornAgainCyclist]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Already done when I got there.  

Looks like you did all the right things, but were just unlucky.
I've always given the crank a 'tap' each way with a mallet after the bolt was removed and before inserting the puller - don't know whether it does any good, but me dad told me to do it, so it must be right.

[Ian H]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Already done when I got there.  

And the washer? But if you didn't have to use massive force, then the threads were worn already.

[David Martin]

Errrm, I'm not seeing the bit where you removed the axle bolts before you screwed the extractor in? 

Already done when I got there.  

And the washer? But if you didn't have to use massive force, then the threads were worn already.

I read it as just snugging the extractor up tight into the crank, before starting to remove it.

Cheap crank extractors are pants. The only one I trust is my Shimano one - all others I have used are teh spawn of Stan.

There is an answer.. Hollowtech II.

..d

[Wibble]

And the washer? But if you didn't have to use massive force, then the threads were worn already.

And the washer too.  It did take some force - next time I will use the mallet suggestion - I guess that breaks any bond that's formed between crank, bb spindle and any dirt.

Not looking forward to seeing how much it's cost my friend 

[Lucky]

Why does he need a new chainset? Surely the thread you stripped is only used for screwing in a crank extractor, and so if you can find a way of getting it off without further damaging it, it will be perfectly re-usable? He just won't be able to use a crank extractor on it in future.

[blackburnrod]

I have a tool which will reform the thread in the crankif it is not terminally damaged.

[Wibble]

Why does he need a new chainset? Surely the thread you stripped is only used for screwing in a crank extractor, and so if you can find a way of getting it off without further damaging it, it will be perfectly re-usable? He just won't be able to use a crank extractor on it in future.

Oooh, didn't think of that.  It's at the LBS now, so I'll pass on the tip.  Might make replacing the next bottom bracket fun thobut. Torslanda and his 4lb Hammer may come in handy...

[StanThomas]

Cheap crank extractors are pants. The only one I trust is my Shimano one - all others I have used are teh spawn of Stan.

I think that's most unfair.

[StanThomas]

Why does he need a new chainset? Surely the thread you stripped is only used for screwing in a crank extractor, and so if you can find a way of getting it off without further damaging it, it will be perfectly re-usable? He just won't be able to use a crank extractor on it in future.

I have exactly the same problem on the non-drive side. I could get it off with a two-legged puller but last time I did something like that, it marked the crank quite badly. Any suggestions on the best tool to use?

[Torslanda]

Remove the bolt and put it back in leaving it loose.

Put it in top gear and set off up a gert big hill or stand on the pedals and 'bounce' the bike as you ride downhill with the pedals level.

Tap it with a mallet, remove the bolt and it should fall off.   

J

[StanThomas]

Remove the bolt and put it back in leaving it loose.

Put it in top gear and set off up a gert big hill or stand on the pedals and 'bounce' the bike as you ride downhill with the pedals level.

Tap it with a mallet, remove the bolt and it should fall off.   

J

Tried that today on a 30km ride. No luck. But it does seem likely that, with the bolt left loose, it'll fall off eventually. Just depends whether I get bored with the wait first. And I have to be sure I keep the wrench on the bike and tape over the bolt  'cos I'm going to look really stupid if it falls off and I can't put it back on to get home.

[hubner]

I'm sure everyone knows this method will damage the crank tapers, so it's only useful if you want to scrap the cranks.

[StanThomas]

I'm sure everyone knows this method will damage the crank tapers, so it's only useful if you want to scrap the cranks.

If I wanted to scrap the cranks I'd cut 'em off with a hacksaw. So, can you suggest a tool, like an automotive puller say, that won't mark the cranks up?