Crank thread stripped: what now?

[A Muzi]

>> [email protected] wrote:
>>> the crank-extractor thread on my left crank (shimano deore aluminium
>>> square taper) is completely stripped.
>>> I have already extracted the crank, but I would like to use it again
>>> and therefore make it "easily" extractable.
>>> Is there any way to cheaply repair it?
>>> What if I buy a self-extracting bolt and sort of "weld" it in place
>>> (is loctite strong enough? the thread is completely gone)

> "David L. Johnson" <[email protected]> wrote
>> If you really don't want to buy a new crank, find a gear puller (this is
>> used in auto repair to pull pulleys and the like off of their shafts) that
>> will fit over the crank. This may damage the crank, but you've already
>> done that.

Mike Jacoubowsky wrote:
> Have you had much success with gear pullers? We've tried them in the past
> and rarely found them to be of much use. Could be that we didn't have the
> right-size gear puller, or wrong technique, but I'd be interested in hearing
> from people who have made good use of them to remove cranks.

We've never found them useful either.
Most gear pullers are 2 or three sided which doesn't work at all well
and can't mount easily on a crank anyway. VAR's 932 is an elegant tool
which worked well until cranks became too wide for it.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[M-gineering]

A Muzi wrote:
but I'd be
>> interested in hearing from people who have made good use of them to
>> remove cranks.
>

If they are to work at all you'll have to keep the legs closed with a
hefty hoseclamp
--
/Marten

info(apestaartje)m-gineering(punt)nl

 

[A Muzi]

> "Mike Jacoubowsky" <[email protected]>
>> Have you had much success with gear pullers? We've tried them in the past
>> and rarely found them to be of much use. Could be that we didn't have the
>> right-size gear puller, or wrong technique, but I'd be interested in hearing
>> from people who have made good use of them to remove cranks.

sergio wrote:
> Not me, Mike. Sorry for disappointing you.
> There was simply not enough room for the jaws.
> On the other hand I do know that a couple of hard-wood wedges hammered
> in place make an excellent puller, yet better if one has heated up a
> bit the crank head.
> Plus, here in Pisa I have very good connections and I know a competent
> machine shop that would implant the elicoil for little money. They
> have done it to a stripped 3ttt handlebar stem that I brought in,
> recently.
> One reservation I would make, however. It might not be easy to bore
> correctly tp prepare for the tap [Andrew, please, put it into English
> 101].
> So, Federico, do not despair.
> Call again next time you are in the neighborhood.

Yes, a threaded insert or coil system works but requires a piloted tap
system or a special tap.

The 'wire' systems cut a non standard thread slightly larger. A coil of
diamond-cross-section wire is spun into that channel, the inside edge of
which becomes your new thread.

Full sleeved insert systems begin with a larger thread, in the case of
crank-specific products with a piloted tap. The inserts are threaded on
both inside and out.

These are common, outside bicycles, for spark plug threads in aluminum
heads and all sorts of repair work. Our aluminum cranks use a relatively
fine thread and relatively a lot of pressure for that small depth, so
one does well to clean the crank thread, lubricate the tool's thread and
double check that no washers are left in place before mounting the tool
securely in the crank.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[A Muzi]

>>>> the crank-extractor thread on my left crank (shimano deore aluminium
>>>> square taper) is completely stripped.
>>>> I have already extracted the crank, but I would like to use it again
>>>> and therefore make it "easily" extractable.
>>>> Is there any way to cheaply repair it?
>>>> What if I buy a self-extracting bolt and sort of "weld" it in place
>>>> (is loctite strong enough? the thread is completely gone)

>>> Sure, the VAR 1010 system is a piloted tap for a larger coarser thread
>>> with a steel insert for the remover, get it machined at any competent LBS.

> "Mike Jacoubowsky" <[email protected]> wrote:
>> Yes, but it's a *left* crank arm, which is relatively cheap, and since he'd
>> like to make it "easily" extractable again, I think having to use a special
>> not-easy-to-find extractor in the future defeats the purpose. Or to put it
>> another way, by the time he pays for having the crank re-tapped *and* the
>> new tool he'll need to remove it, he'll have spent more than he would have
>> for a new crank arm..

Nate Knutson wrote:
> Just checked and actually, the VAR system puts an oversized
> proprietary self-extractor.on the crank. The kit comes with a seperate
> crank puller for the shop.
> What's the point, compared to the Stein?

So do ReCoil and HeliCoil. VAR's nicely made, easy to use.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[[email protected]]

On Sep 20, 2:10 pm, A Muzi <[email protected]> wrote:
> Our aluminum cranks use a relatively
> fine thread and relatively a lot of pressure for that small depth, so
> one does well to clean the crank thread, lubricate the tool's thread and
> double check that no washers are left in place before mounting the tool
> securely in the crank.

That's at least three ways that job can go wrong <g> and another vote
for replacing a crank that has one side's extractor threads
stripped-- IOW, start over, new.

Save the good pieces, of course.

Would that also be a good reason to lube the tapered flats on the BB
axle before mounting the crank arms? (Thread was kinda petering out,
looked like) --D-y

 

[A Muzi]

Mike Jacoubowsky wrote:
> but I'd be
>>> interested in hearing from people who have made good use of them to
>>> remove cranks.

M-gineering wrote:
> If they are to work at all you'll have to keep the legs closed with a
> hefty hoseclamp

[edited attribution]
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[[email protected]]

> If you really don't want to buy a new crank, find a gear puller (this is
> used in auto repair to pull pulleys and the like off of their shafts)
> that will fit over the crank. This may damage the crank, but you've
> already done that.


You would be better off using a pitman arm puller, which is used to
removed ball joints from cars. they come in various sizes, and the
reason they work better than a gear puller is that the arms are
imobile. I just used it to remove the left crank on an old bike with
smashed up threads. didnt mar the crank at all. just reinsert the bolt
a few turns, so the bolt from the puller has something solid to push
against. you can find an example here, http://www.thetoolwarehouse.net/shop/KD-2289.html

also, places such as checker/shucks/kragen auto parts rents tools for
dirt cheap. you probably could talk them into letting you use it for
free if you bring your bike with you.

 

[sergio]

On 25 Set, 18:58, [email protected] wrote:

> You would be better off using a pitman arm puller, which is used to
> removed ball joints from cars.

Quite funny reading this.
I have known for more than twenty years a VERY GOOD Mercedes Benz
mechanic and have watched him remove such ball joints from my 200D.
He never used the proper tool.

Always did he knock really hard with a hammer, while holding another
heavy mass against the joint on the opposite side.

Sergio
Pisa

 

[!Jones]

On Tue, 25 Sep 2007 16:58:27 -0000, in rec.bicycles.tech
[email protected] wrote:

>You would be better off using a pitman arm puller...

Agreed. But a good one costs a significant fraction of the cost of a
new crank arm... so bite the bullet!

The OP probably screwed in a TA puller. Tell me why (oh, why!!!) did
they make them so f**king close?

That's obvious: to sell cranks, of course!

Jones