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Thread: South Bend Heavy 10 Chuck Problem

  1. #1
    Join Date
    Jun 2006
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    NE NC/SE Wisc.
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    Default South Bend Heavy 10 Chuck Problem

    We have a South Bend Heavy 10 lathe in a common area which can be used by several people. The last person to use the lathe left the four jaw chuck on the lathe. The chuck is a screw on/off and the chuck must have been tightened by an 800 lb. gorilla! I've soaked the threads with penetrating oil and it has sat for 24 hours. I normally engage the back gear to hold the shaft stationary while the lathe chuck is unscrewed with a wrench on one of the chuck jaws. The chuck is on so tight, I afraid I will break the teeth on the back gear if I put too much torque on the chuck to try to break it free. I've already bent a 1/2" by 1/2" foot long bar trying to break the chuck free. Does anyone have suggestions on how to remove the stuck chuck without breaking the back gear teeth? Thanks in advance.
    Bill

    Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

    Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

  2. #2
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    Default

    Dont use the back gear!! JR
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  3. #3
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    Aug 2004
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    Default

    I got my 10l knowing one or two teeth were missing from the BG. It is a matter of grasping the spindle proper then think about short rotational impacts, what do they call those.

    So wrench up the 1/2" air drive with a 1/2 sawed off blank. Chuck it up in the lathe chuck and give it a couple hits with the air gun. Light taps (make sure you have your directions correct).

    It might pop right off. JR
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  4. #4
    Join Date
    Jan 2016
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    227

    Default

    stick an ice cube in the spindle.

    back gear teeth on a southbend 9 are 16 dimetrical pitch 5/8" wide, made from 30,000 psi cast iron can handle 40-50 foot pounds continuously, the cast iron teeth have a good chance of breaking above 100 foot pounds, are nearly guaranteed to break at 150 foot pounds of torque... know your limits.
    Last edited by johansen; 09-06-2019 at 04:25 AM.

  5. #5
    Join Date
    Aug 2012
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    Warwickshire, UK
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    Does the spindle have a collar visible between the backplate and the bearing housing? If so, you could try drilling a blind hole into the collar and making a Cee spanner to fit. Worst case scenario is to take the chuck off the backplate and machine the backplate to dust. Don't risk the backgears any more than you have done already.

    When I was reconditioning my UK made Raglan, (these seemed to be susceptible to broken back gear teeth) and had the spindle out, I machined 2 flats on the collar and made a big spanner out of steel plate. With the end of the spanner resting against the bed casting, a smart tap on a spanner on a chuck jaw always worked. Then the big plate spanner jumped off, and fell on my feet----.
    'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

  6. #6
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    Jan 2013
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    Default

    Yeah, don't break the back gear. Much better not to use it for this. I wonder if there is debris in the threads..

    This question comes up regularly. Lots of good info out there, and there is some awful advice mixed in! There was a thread on PM in the past 6 mos where someone had purchased an old lathe and the chuck had been on for potentially decades. That was a great read, as the OP tried various techniques. I couldn't locate the thread. There were also concerns that there might be buried set screws locking the chuck on. His chuck was surely much more stuck than yours, fortunately.

    There is the fundamental question of whether smooth torque can solve this, or whether a more abusive impact approach - whether hammer or otherwise - is required. Much better to be smooth about it, especially on a small lathe like this.

    He clamped a bar to the opposite end of the spindle to prevent it from turning. His first bar was hollow, like a stop sign, and the flex was too great for it to work - it was feeble. Bolts were undersize, clamp material was aluminum. He eventually had to upgrade all that. But something light might work for you.

    You can clamp a piece of metal in the chuck, and either allow it to rest against the bed and fix the chuck, or you can use it to turn the chuck.

    Have you tried a strap wrench on the chuck and on a spindle gear? They are sorta feeble, but possibly.

  7. #7
    Join Date
    Dec 2018
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    Default

    the youtube guy Mrpete222 did several videos on just that subject.
    one way was to make a internal mandrel to go up inside the spindle and hold it.
    And, use a impact hit rather than just a cheater bar to break loose the thread

  8. #8
    Join Date
    May 2015
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    Coral Springs, FL
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    Default

    Take a look at this post: https://www.hobby-machinist.com/thre...1/#post-555123

    Using the back gear to lock the spindle to remove a stuck chuck is almost guaranteed to break off teeth on the gear. Build the spindle crank and you'll be able to lock the spindle without destroying the back gear.

    In the future, cut a washer out of wax paper or parchment paper and place that between the chuck and the spindle face. This is a trick used by the British for their lathes on ships to prevent locked chucks.

  9. #9
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    Thanks for the ideas. It is now off to the shop to try to see which one will work the best. Paper spacer on spindle shaft will be mandatory in the future!
    Bill

    Being ROAD KILL on the Information Super Highway and Electronically Challenged really SUCKS!!

    Every problem can be solved through the proper application of explosives, duct tape, teflon, WD-40, or any combo of the aforementioned items.

  10. #10
    Join Date
    May 2015
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    Somerset UK
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    Default

    The person who last tightened the chuck need not have been a gorilla, if you screw up the chuck until it is 1/4 turn from tight and then spin it on, the inertia will do the rest. Rather than an ice cube in the spindle, you might try heat from a heat gun blowing through the spindle bore. If the length of the spindle threads to the register face increased even a tiny bit, the chuck might not be so tight. I have long since stopped jarring the threads loose on the Smart & Brown and prefer using a strap wrench. If you jam the back gear with a wad of cloth and keep a steady pressure on the chuck with a strap wrench while heating the bore of the spindle, it might work.

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