Stripped Crank arm threads

Discussion in 'Cycling Equipment' started by Mike Kennedy, Sep 13, 2003.

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  1. Mike Kennedy

    Mike Kennedy Guest

    Is there a way to pull a crank arm off if the threads have been stripped? I assume that the LBS has
    some way to do this, but is there some way for me to do the work? Can stripped threads be
    re-threaded?

    Regards,

    Mike
     
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  2. S. Anderson

    S. Anderson Guest

    "Mike Kennedy" <[email protected]> wrote in message news:[email protected]...
    > Is there a way to pull a crank arm off if the threads have been stripped? I assume that the
    > LBS has some way to do this, but is there some way for me to do the work? Can stripped threads
    > be re-threaded?
    >
    > Regards,
    >
    > Mike
    >
    >

    There are various methods. You can try riding it without the crank bolt, heating the arm up and
    yanking, getting a drive gear puller from an auto parts store, or just plain beating the hell out of
    it. You will not be able to re-thread the threads that are there and have them work correctly. If
    you go the gear puller route and it's successful, I'd just put it back on and use that puller to
    remove it from now on.

    Cheers,

    Scott..
     
  3. "S. Anderson" wrote:
    >
    > "Mike Kennedy" <[email protected]> wrote in message
    > news:[email protected]...
    > > Is there a way to pull a crank arm off if the threads have been stripped? I assume that the
    > > LBS has some way to do this, but is there some way for me to do the work? Can stripped
    > > threads be re-threaded?
    > >
    > > Regards,
    > >
    > > Mike
    > >
    > >
    >
    > There are various methods. You can try riding it without the crank bolt, heating the arm up and
    > yanking, getting a drive gear puller from an auto parts store, or just plain beating the hell out
    > of it. You will not be able to re-thread the threads that are there and have them work correctly.

    Cranks can be rethreaded, but you'll have to use an oversize puller from then on

    --
    Marten
     
  4. S. Anderson

    S. Anderson Guest

    "M-Gineering import & framebouw" <[email protected]> wrote in message
    news:[email protected]...
    >
    > Cranks can be rethreaded, but you'll have to use an oversize puller from then on
    >
    >
    > --
    > Marten

    I've tried this route before and not had great success. Usually I go through the trouble of
    re-threading to the larger Park puller size only to have the threads pull out when I try to remove
    the crank again. Maybe I had poorly made tap or maybe I can't cut threads very well! In any event,
    it is an alternative if you can get the threads cut well.

    Cheers,

    Scott..
     
  5. Garry Broad

    Garry Broad Guest

    On Sat, 13 Sep 2003 07:53:42 -0700, "Mike Kennedy" <[email protected]> wrote:

    > Is there a way to pull a crank arm off if the threads have been stripped? I assume that the LBS
    > has some way to do this, but is there some way for me to do the work? Can stripped threads be
    > re-threaded?

    Amusing...not your post, but what it reminded me of. I serviced/rebuilt a mate's mountain bike this
    week, and came across this very problem. The left crank came off no problem, but the right [drive]
    side was a real stubborn so and so. Even with some heat, it just would not budge. So in the end it
    was a battle between my strength and the threads on the crank!! So....out came the angle grinder. I
    cut a grove about 2mm parrallel to the taper of the drive spindle [without damaging it], got the
    hammer our, gave it a few bashes to weaken the already weakened alloy, and off it came. There's
    something theraputic about an angle grinder :)

    In all honesty, if the threads are stripped, I'd suggest it's reached the end of it's life,
    regardless of the fact that it might be a perfectly good crank. You never know when you might want
    to service the BB, or do other work on the crankset. Much better to have all the 'service points' in
    good order.

    GarryB
     
  6. Werehatrack

    Werehatrack Guest

    On Sat, 13 Sep 2003 07:53:42 -0700, "Mike Kennedy" <[email protected]> may have said:

    > Is there a way to pull a crank arm off if the threads have been stripped?

    Several. On the left (non-drive) side, a gear puller will usually do the job. If it's on the drive
    side, and if the chainrings allow enough access to be able to get the jaws of an ordinary gear
    puller behind the hub, then that's probably your first approximation. If the chainrings can't be
    gotten out of the way, or if it's a five-arm spider crank, you probably can't use this trick.

    >I assume that the LBS has some way to do this, but is there some way for me to do the work? Can
    >stripped threads be re-threaded?

    If the crank is supposed to be usable when you're done, then it may be better to take it to the lbs,
    as a certain amount of finesse may be required. If you want to try it yourself, then the suggestions
    already posted (heating the hub with a propane torch, riding with the bolt loose or off, etc) all
    have the potential to remove the arm, *but* they also all have the potential to damage the crank as
    well. As was noted, Park makes an oversize puller, and there's a tap to cut the corresponding
    threads, but this is one of those areas where unless you're pretty good with a big tap, there's more
    than a trivial chance that the attempt will fail.

    In order of what I'd try:

    Gear puller.

    Heat.

    Ride with bolt loose.

    Yank whole crank and BB off bike, take to machine shop, and have them use a press to pop the arm off
    the shaft. (In my case, of course, the press is a whole lot closer.)

    Use potentially destructive Big Hammers in a persuasive manner. (NOT recommended for those who are
    not familiar with the techniques!)

    --
    My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
    don't respond to something, it's also possible that I'm busy.
     
  7. Mike Kennedy

    Mike Kennedy Guest

    Thanks everyone for these suggestions! To be honest I had not thought about a gear puller :( I also
    do not really care if I damage the arm (non drive side). I would try the grinder, but my wife will
    not let me have one
    :)

    Mike

    "Werehatrack" <[email protected]> wrote in message
    news:[email protected]...
    > On Sat, 13 Sep 2003 07:53:42 -0700, "Mike Kennedy" <[email protected]> may have said:
    >
    > > Is there a way to pull a crank arm off if the threads have been stripped?
    >
    > Several. On the left (non-drive) side, a gear puller will usually do the job. If it's on the drive
    > side, and if the chainrings allow enough access to be able to get the jaws of an ordinary gear
    > puller behind the hub, then that's probably your first approximation. If the chainrings can't be
    > gotten out of the way, or if it's a five-arm spider crank, you probably can't use this trick.
    >
    > >I assume that the LBS has some way to do this, but is there some way for me to do the work? Can
    > >stripped threads be re-threaded?
    >
    > If the crank is supposed to be usable when you're done, then it may be better to take it to the
    > lbs, as a certain amount of finesse may be required. If you want to try it yourself, then the
    > suggestions already posted (heating the hub with a propane torch, riding with the bolt loose or
    > off, etc) all have the potential to remove the arm, *but* they also all have the potential to
    > damage the crank as well. As was noted, Park makes an oversize puller, and there's a tap to cut
    > the corresponding threads, but this is one of those areas where unless you're pretty good with a
    > big tap, there's more than a trivial chance that the attempt will fail.
    >
    > In order of what I'd try:
    >
    > Gear puller.
    >
    > Heat.
    >
    > Ride with bolt loose.
    >
    > Yank whole crank and BB off bike, take to machine shop, and have them use a press to pop the arm
    > off the shaft. (In my case, of course, the press is a whole lot closer.)
    >
    > Use potentially destructive Big Hammers in a persuasive manner. (NOT recommended for those who are
    > not familiar with the techniques!)
    >
    > --
    > My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
    > don't respond to something, it's also possible that I'm busy.
     
  8. I used a cheap (thick) hatched head, no handle, as a wedge to pound into the space between the BB
    and the crank arm. Alternated the the position around the crank, and pounded on the wedge with a 3
    pound steel mallet.

    Worked OK. Crank arm went shooting off after about 2-3 minutes of carefull work.

    This was a beater bike with a sturdy cro mo frame and bottom bracket.

    Not a good idea for lightweight alloy framed bikes or those without a enough steel surface on the BB
    shell to guard the BB shell of the bike. Not a good idea if your using a Ti Bottom bracket. Wear
    goggles in case something chips and , of course, handle the hatchet head with care and don't strike
    it unless it is planted with the crank squarely pressing against the middel of the wedge (would not
    want it to angel off and slip out of the crank/BB space).

    Consider bracing the BB against the ground with wood blocks to prevent the tires from abosorbing the
    effect of the hammer blows. Take care not to crush any cable routing doohickeys underneath the
    bottom bracket. Could also turn it upsde down, insert a beater seatpost without a saddle, and let
    the seat post contact the hard ground. Make sure seat post does not get pushed in all the way during
    pounding, allowing the seat tube junction / lug to get damaged.

    "Mike Kennedy" <[email protected]> wrote in message
    news:<[email protected]>...
    > Is there a way to pull a crank arm off if the threads have been stripped? I assume that the LBS
    > has some way to do this, but is there some way for me to do the work? Can stripped threads be
    > re-threaded?
    >
    > Regards,
    >
    > Mike
     
  9. Rick Onanian

    Rick Onanian Guest

    On Sat, 13 Sep 2003 13:08:58 -0700, Mike Kennedy <[email protected]> wrote:
    > Thanks everyone for these suggestions! To be honest I had not thought about a gear puller :( I
    > also do not really care if I damage the arm (non

    An auto parts store with a tool loan program ought to do for the gear puller.

    > drive side). I would try the grinder, but my wife will not let me have one
    > :)

    What business does she have intruding on your domain? We're talking about Tools!

    Buy the angle grinder. If it's the price that's the issue, look for a bottom-of-the-retail-chain
    discounter like Ocean State Job Lot; those places tend to have angle grinders for $15...

    > Mike
    --
    Rick Onanian
     
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