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Hub damage from cheap crank extractor

Started by semach.the.monkey · · Last activity · 10 posts · 335 views

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01 / Original postHub damage from cheap crank extractorsemach.the.monkey · 11 Aug 2006 02 / This pagePosts 1–10Page 1 of 1 · chronological order 03 / Latest replyPost #10Semach.the.monkey · 13 Aug 2006

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rec.sport.unicycling
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11 August 2006
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13 August 2006
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semach.the.monkey
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  1. Original post
    semach.the.monkey
    Archived post
    #1

    Ok, I guess this is all my own fault for being a tight [censored]. However,
    after borrowing a crank extractor a few times (Thanks Roland), I
    thought it was about time I bought my own one. I looked about on the
    net, and found I could get one from eBay for half the price of the UDC
    one. Bargain, I thought!

    However, I got around to using it today, and found that the kind of
    metal it is made from is only slightly firmer than chocolate on a warm
    day. If it had been exactly the same consistancy as chocolate, then I
    would have just ended up with some goo in my cranks. Unfortunatly, it
    was just tough enough to try to work it's way in to the hole in the end
    of the hub, and damage the thread.

    So, I wasn't able to get the crank off, and, more worringly, I can't
    get the bolt back in.

    Has anyone else had this happen to them? How would you suggest I try
    to repair the hub? Would running a Tap or Dye (can never remember
    which is which) in to the hub re-cut the thread to what it was, or is
    this likely to do more damage? If the hole is totally buggered, and I
    don't want to buy a new hub, would I be best off getting the crank
    welded on and accept the fact that I won't be able to change it again?

    Cheers

    STM

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  2. rob.northcott
    Archived post
    #2

    It sounds like it's just damaged the start of the thread. The crank
    bolt goes quite a long way in, so if you clean up the start of the
    thread with a tap (it'll be a normal metric thread, probably M8) so you
    can get the bolt in, it'll probably be fine. I doubt "your hole is
    completely buggered" (yak yak).
    How cheap was your crank extractor? They don't normally cost more than
    five or six quid, and that's for a decent quality one like a Cyclo or
    Park.

    Rob

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  3. semach.the.monkey
    Archived post
    #3
    rob.northcott said:


    How cheap was your crank extractor? They don't normally cost more than
    five or six quid, and that's for a decent quality one like a Cyclo or
    Park.

    It was the princely sum of three British pounds. See item 150019722714
    on eBay to see what you should avoid.

    STM

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  4. rob.northcott
    Archived post
    #4

    OK, that is perhaps a bit too cheap. Save up an extra three quid and
    get yourself a decent one 🙂

    I doubt you've done any real damage though - just borrow an M8 tap
    (check it is M8 first, but it probably is) and clean up the end of the
    thread and you should be fine.

    Rob

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  5. nickjb
    Archived post
    #5

    It should have only damaged the first turn or so of thread so you could
    probably just clean it up a bit. Use a small file or hard pointy thing
    like a scribe, place the tip inside the good thread further down the
    hole and work it out to the top by effectively unscrewing it. A tap
    might work but it'll probably make it worse. It's usually an M8 fine
    thread (not std M8) so it's unlikely you'll have one lying about anyway
    🙂

    Shimano make an excellent crank extractor

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  6. rob.northcott
    Archived post
    #6

    OK, you could probably clean the thread up the way Nick says. It's just
    that I *do* have things like taps "lying around" so I tend to use them.
    Either way, get a better puller! (even ShimaNO if you must)

    Rob

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  7. Semach.the.monkey
    Archived post
    #7

    "nickjb" wrote in message ...

    Quoted message said:

    It should have only damaged the first turn or so of thread so you


    could

    Quoted message said:

    probably just clean it up a bit. Use a small file or hard pointy


    thing

    Quoted message said:

    like a scribe, place the tip inside the good thread further down the
    hole and work it out to the top by effectively unscrewing it. A tap
    might work but it'll probably make it worse. It's usually an M8 fine
    thread (not std M8) so it's unlikely you'll have one lying about


    anyway

    Quoted message said:

    🙂

    Well, that's worked fine. A combination of subtle filing, pulling with
    a sharp hardened pointy thing, slightly rounding the end of the bolt,
    and decent light to see by, and I've managed to get it all back together
    again.

    I'm still left with the 125mm cranks on though, until I can save up
    enough pennies to treat myself to a top of the range one for £6.50!

    STM

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  8. skrobo
    Archived post
    #8
    Semach.the.monkey said:

    "nickjb" wrote in message ...

    Quoted message said:

    It should have only damaged the first turn or so of thread so you


    could

    Quoted message said:

    probably just clean it up a bit. Use a small file or hard pointy


    thing

    Quoted message said:

    like a scribe, place the tip inside the good thread further down the
    hole and work it out to the top by effectively unscrewing it. A tap
    might work but it'll probably make it worse. It's usually an M8 fine
    thread (not std M8) so it's unlikely you'll have one lying about


    anyway

    Quoted message said:

    🙂

    Well, that's worked fine. A combination of subtle filing, pulling with
    a sharp hardened pointy thing, slightly rounding the end of the bolt,
    and decent light to see by, and I've managed to get it all back
    together
    again.

    I'm still left with the 125mm cranks on though, until I can save up
    enough pennies to treat myself to a top of the range one for £6.50!

    STM

    have you tried the "hammer off" method?
    i find it to work quite well, you just take the bolt out, get a hammer,
    and a punch(of some sort, large bolts work well) . you then stick the
    punch through the spokes (w/ a rag or something on the crank to keep it
    pretty) and hit the other end w/ a hammer, being careful not to hit the
    spokes, if you choose to do this it may take a few blows before it
    comes off, and you must be careful of where the crank flys off to. and
    one more thing, get the punch as close to the axle as possible, you
    also have to keep the pedal off the ground, try it if you want, but its
    totally up to you

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    UNICYCLES WITH BANANNA SEATS FOR CHRIST!
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    sorta hardcore for 4 months

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  9. adelman
    Archived post
    #9

    The thread is an M8 x 1; a standard M8 is a wider pitch M8 x 1.25. An M8
    x 1 tap is somewhat rare; in the USA you can buy them from
    www.biketoolsetc.com.

    The problem might not be the quality of the extractor, but rather the
    age. Older extractors are designed for "nut type" cranks only and do
    not have a floating tip which is designed to protect the "bolt type"
    threads on the axle. The use of a domed-end extractor on bolt-type
    axles will almost always damage the threads.

    +-------------------------------------------------------------------+
    |Filename: Picture 1.png |
    |Download: http://www.unicyclist.com/attachment/14517 |
    +-------------------------------------------------------------------+

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  10. Semach.the.monkey
    Archived post
    #10

    "adelman" wrote in message ...

    Quoted message said:

    The problem might not be the quality of the extractor, but rather the
    age. Older extractors are designed for "nut type" cranks only and do
    not have a floating tip which is designed to protect the "bolt type"
    threads on the axle. The use of a domed-end extractor on bolt-type
    axles will almost always damage the threads.

    Ah, that would explain it. I thought it was just a poorly designed bit
    of kit. Looking at that picture, I can see that it was probably well
    designed, but for a "nut type" crank.

    I wish I'd seen that _before_ I tried to do this :-(

    STM

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