Broken Screw Extraction: 4 mm?

Discussion in 'Cycling Equipment' started by x, Sep 26, 2003.

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  1. x

    x Guest

    I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    ("Easy-Out"?) and unscrew the broken part.

    But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    point, but is only about 4mm in diameter.

    Seems like there's a real good chance of drilling into the bearing's threads by accident.

    Has anybody got experience with extracting a screw this small?
    -----------------------
    PeteCresswell
     
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  2. Werehatrack

    Werehatrack Guest

    On Fri, 26 Sep 2003 22:56:31 GMT, "(Pete Cresswell)" <[email protected]> may have said:

    >I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    >("Easy-Out"?) and unscrew the broken part.
    >
    >But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    >point, but is only about 4mm in diameter.
    >
    >Seems like there's a real good chance of drilling into the bearing's threads by accident.
    >
    >Has anybody got experience with extracting a screw this small?

    You may be able to coax it out with a machinist's pick, simply pushing it around to unscrew it. It's
    unlikely that the screw is corroded, so the broken piece will probably come out without much hassle.
    If it resists gentle persuasion, a gunsmith might be a good bet for assistance if the lbs isn't
    willing or able to tackle it.

    --
    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.
     
  3. Jobst Brandt

    Jobst Brandt Guest

    Pete Cresswell writes:

    > I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    > ("Easy-Out"?) and unscrew the broken part.

    Don't do it.

    > But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    > point, but is only about 4mm in diameter.

    How did the screw break? If it was because it was going in tight, then it's time to order a new
    part. If it was just over-tightened, it should come loose by tapping on it with a tiny hammer and
    tool pick in a counter-clockwise direction. Easy outs have limited application and for small screws
    it's not and Easy-out but an easy-in... forever.

    > Seems like there's a real good chance of drilling into the bearing threads by accident.

    > Has anybody got experience with extracting a screw this small?

    As was mentioned, gunsmiths do that sort of stuff as do good machine shops that do precision work.

    Jobst Brandt [email protected]
     
  4. x

    x Guest

    RE/
    >How did the screw break? If it was because it was going in tight, then it's time to order a
    >new part.

    The hub kept weeping oil in spite of gasket changes so, genius that I am, I figured I'd turn up the
    torque a little - like from the recommended 25 inch pounds to fifty....

    It sheared when it wasn't all the way in. "Going in hard" sounds like an apt description, but a
    couple of them go in that way on both of my Rohloff hubs. I'd call it a defective screw.

    The gunsmith suggestion sounds good. There are certainly more (or at least more easy-to-find...)
    gunsmiths around there than there are machine shops.

    I think I've finally fixed the oil leakage - on the good hub, at least - by coating the gaskets with
    Form-A-Gasket before reassembly. Did about 20 miles today which should have had oil dripping out,
    but there was nada. Pulled the shift box off and there was a little inside, but I'm hoping that's
    just residual from beforehand.
    -----------------------
    PeteCresswell
     
  5. Werehatrack

    Werehatrack Guest

    On Sat, 27 Sep 2003 00:38:49 GMT, "(Pete Cresswell)" <[email protected]> may have said:

    >Jobst Brandt inquired:
    >
    >>How did the screw break? If it was because it was going in tight, then it's time to order a
    >>new part.
    >
    >The hub kept weeping oil in spite of gasket changes so, genius that I am, I figured I'd turn up the
    >torque a little - like from the recommended 25 inch pounds to fifty....
    >
    >It sheared when it wasn't all the way in. "Going in hard" sounds like an apt description, but a
    >couple of them go in that way on both of my Rohloff hubs. I'd call it a defective screw.

    This is, of course, engaging in closing the barn door after the horse has gone, but...

    Experienced mechanic's rule about a screw going in hard: In most cases, if it doesn't easily go all
    the way to the point of head contact with the part, either you're using the wrong screw, it's
    cross-threaded, the threads were buggered already, or there's foreign material in the hole. When the
    screw goes in hard, STOP. Pull it back out, grab the magnifier and the penlight, and find out why.
    Fix the problem before it has a chance to do what has happened to you.

    --
    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.
     
  6. Jim Beam

    Jim Beam Guest

    > I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    > ("Easy-Out"?) and unscrew the broken part.

    not just theory! i've done this procedure on similar non-bike components of this size and it
    definitely works.

    i do /not/ however recommend doing it yourself unless you have access to a pillar drill and a
    machinists vice. with a screw this size, you have to drill dead center and perfectly axial. if you
    don't have the tools, take it to a shop that does. you basically have one chance to do the job
    properly so you can't afford to mess it up.

    jb
     
  7. x

    x Guest

    RE/
    > either you're using the wrong screw, it's cross-threaded, the threads were buggered already, or
    > there's foreign material in the hole.

    In this case, I think it's buildup of a blue substance that Rohloff applies to about a quarter-inch
    of the threads on each of these screws. Looks like blue LocTite, but it's hardened already.
    -----------------------
    PeteCresswell
     
  8. Jim Beam

    Jim Beam Guest

    > In this case, I think it's buildup of a blue substance that Rohloff applies to about a
    > quarter-inch of the threads on each of these screws. Looks like blue LocTite, but it's hardened
    > already.

    if that's the case, try heat when you're extracting. the bond strength of loctite drops off rapidly
    when heated. on "blue" loctite, heating to 232C is recommended for disassembly.

    http://65.213.72.112/tds5/docs/242.pdf
     
  9. Phil Brown

    Phil Brown Guest

    >Has anybody got experience with extracting a screw this small?
    >-----------------------
    >PeteCresswell

    Find out who your local kotorcycle shop uses for this sort of thing. There is a process whose name
    escapes me using electrical current to remove the broken screw. phil brown
     
  10. A Muzi

    A Muzi Guest

    (Pete Cresswell) wrote:

    > I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    > ("Easy-Out"?) and unscrew the broken part.
    >
    > But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    > point, but is only about 4mm in diameter.
    >
    > Seems like there's a real good chance of drilling into the bearing's threads by accident.
    >
    > Has anybody got experience with extracting a screw this small?

    If it's hardened ( sounds like it may be) then slitting the top then using a screwdriver is better.

    --
    Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
     
  11. Werehatrack

    Werehatrack Guest

    On Sat, 27 Sep 2003 22:31:53 -0500, A Muzi <[email protected]> may have said:

    >(Pete Cresswell) wrote:
    >
    >> I know the theory: drill a hole down the center of the broken off screw, then insert the
    >> extractor ("Easy-Out"?) and unscrew the broken part.
    >>
    >> But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    >> point, but is only about 4mm in diameter.
    >>
    >> Seems like there's a real good chance of drilling into the bearing's threads by accident.
    >>
    >> Has anybody got experience with extracting a screw this small?
    >
    >
    >If it's hardened ( sounds like it may be) then slitting the top then using a screwdriver is better.

    Good point; I've done the slitting with a diamond disc in a Dremel. (Not too useful if the break
    point is below the surface of the part, though.)

    --
    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.
     
  12. x

    x Guest

    RE/
    >Just remembered the name of the process-spark erosion.

    Looks like these guys do it:

    http://www.wadedynamics.com/broken_tool_removal.htm

    But I'm starting to suspect it would be cheaper to get a new bearing assembly - postage both ways,
    removal costs....plus there's at least one other hole that's "hard" - although it hasn't caused a
    bolt to shear yet...
    -----------------------
    PeteCresswell
     
  13. Werehatrack

    Werehatrack Guest

    On Sun, 28 Sep 2003 23:21:33 GMT, "(Pete Cresswell)" <[email protected]> may have said:

    >But I'm starting to suspect it would be cheaper to get a new bearing assembly - postage both ways,
    >removal costs....plus there's at least one other hole that's "hard" - although it hasn't caused a
    >bolt to shear yet...

    Time to chase those threads, then, if you get the busted bolt out.

    Sometimes a threaded hole will need cleaning out even when you can't think of a single reason why
    that should be the case. Sometimes it will strip for no obvious reason, too, particularly in
    aluminum. (That's why I keep more than 20 sizes of helicoil and timesert kit in the toolbox; I just
    never know when I'll need one.)

    --
    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.
     
  14. Rick Onanian

    Rick Onanian Guest

    On Sat, 27 Sep 2003 22:31:53 -0500, A Muzi <[email protected]> wrote:
    >If it's hardened ( sounds like it may be) then slitting the top then using a screwdriver is better.

    I wanted to write that reply, but I couldn't think of a way to slit the top of a 4mm screw, unless
    it sticks out. The OP sounded like the screw head was even or recessed.

    For a larger screw, or one whose head sticks out, it's easy enough to notch it with a dremel.

    --
    Rick "Probably visualizing it wrong" Onanian
     
  15. Spider

    Spider Guest

    "(Pete Cresswell)" <[email protected]> wrote in message news:<[email protected]>...
    > I know the theory: drill a hole down the center of the broken off screw, then insert the extractor
    > ("Easy-Out"?) and unscrew the broken part.
    >
    > But this one in in one of the main bearings of a Rohloff hub. It's broken off right at the entry
    > point, but is only about 4mm in diameter.
    >
    > Seems like there's a real good chance of drilling into the bearing's threads by accident.
    >
    > Has anybody got experience with extracting a screw this small?

    Yes. I drilled it out with a reverse-twist bit. 3/16ths, IIRC. What is that, close to 4mm, right?
    But those bits are hard to find, especially that small. I was lucky to have a set left over from a
    bunch my dad had way back when he was a machinist for Boeing. I would suspect that from their
    rarity, they would also be expensive. As compared to a Speedhub, not so much. :)

    When the bit "bit", the screw just screwed right out. Since the top of the screw was a little domed
    (but not enough to cut a slot) I used a Dremel with a dental burr to make a small dent so the bit
    wouldn't wander.

    I think the best choices have already been mentioned: send it back for service, or take it to a gun
    shop. Those gun guys really can do quite amazing work.

    Spider
     
  16. x

    x Guest

    RE/
    >The OP sounded like the screw head was even or recessed.

    Yes. Just a hair recessed.
    -----------------------
    PeteCresswell
     
  17. John Everett

    John Everett Guest

    On Mon, 29 Sep 2003 21:23:59 GMT, "(Pete Cresswell)" <[email protected]> wrote:

    >RE/
    >>The OP sounded like the screw head was even or recessed.
    >
    >Yes. Just a hair recessed.

    One fairly exotic solution I've seen used, particularly if the (steel) screw is threaded into
    aluminum, is to tack weld a welding rod to the end of the screw and then back out the whole thing
    with a pair of Vise-Grips. A good welding shop should be able to handle this.

    jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3
     
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