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Thread: 4-jaw removal cornfusalment

  1. #1
    tony ennis Guest

    Default 4-jaw removal cornfusalment

    Ok, this 4-jaw hasn't been off the lathe in 2 years at least - that's when the previous owner passed. And there were no additional chucks or faceplates. I can only conclude that this 4-jaw may have been on the lathe for a very long time.

    How do I get it off? I've thought about it so much I'm completely confused. It's a Craftsman 12".

    The chuck needs to be spun clockwise to be removed, yes?

  2. #2
    Join Date
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    Not sure but the cincinatti at school has a taper-key spindle and the chuck un-threads counter clockwise. Also i think the southbends with threaded spindle noses were right hand thread so you spin the chuck counter clockwise to get it off but i've never worked with one...

  3. #3
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    I don't know the Craftsman 12", but I'm pretty sure they were all threaded spindles. So, there should be some means to lock the spindle against rotation. Then chuck should have some feature for attaching a spanner or some sort of bar to turn it counter-clockwise (standard right hand thread) and unscrew the chuck. Don't drop it on the ways!

    If it's been on there a long time, it may be necessary to get more "serious" with it. I've head of folks putting a board under the chuck to protect the ways when/if it drops, then clamping a board in the chuck jaws, extending from one side over the ways. They then run it backward in back gear to break them loose.

  4. #4
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    Errr,no.the chuck needs to be turned anti-clockwise for removal.If it was the other way,your chuck would spin of at the first sign of a load on it.
    That is to say,if your standing in front of the lathe,with the headstock on your left,spin the chuck towards you.If possible,lock the geartrain,or at least in the lowest gear possible.Chuck a piece of scrap steel in the jaws,so it sticks out beyond the chuck.Hit this bit with a good size hammer,and it should free up.
    If it doesn't come off,spray wd-40 or similar on spindle thread,and leave overnight.Should come off nicely in the morning.
    If it doesn't,I'm out of ideas.
    Hans

  5. #5
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    Jul 2003
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    btw.Baddog's point about a board on the ways is a very good one.I use a cheap polypropylene cutting board for this very purpose.
    Hans

  6. #6
    Join Date
    Feb 2005
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    If you put it in back gear and put too much pressure on the gears you may break a tooth on the backgear. If I was removing a stuck 4 jaw chuck I would put an inch bar in the chuck and use an eight point socket with an air wrench after soaking it for a week or so with liquid wrench or a similar penetrating oil. I would use a strap wrench on the drive pully instead of back gear. If all else fails you may have to remove the chuck from the backplate and turn it off.
    my two cents worth, I would interested to know how you finally get the chuck off.
    Herm Williams

  7. #7
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    The chuck is threaded on with a right hand thread and is removed by turning counterclock wise as matador said.

    Put it in back gear and run one of the jaws out to the OD of the chuck. Take an 8" +/- long piece of 3/4" key stock or something similar and lay one end of it flat on the face of the chuck perpendicular to the jaw at the outer edge of the face. Hit it smartly with 1 or 2 pound hammer. A few hits should do it. Be sure the end of the bar on the jaw is square and flat on the jaw. It is important to hit the jaw at the face of the chuck, not away from the face.

    This is the way it is done in almost all machine shops. But if you are a purist and fanatic then there are ways to spend hours and/or days to remove it.

    EDIT: You can use the lowest gear without the back gears and sometimes it will break loose. As mentioned in following posts, the back gears are sometimes easy to break.
    Last edited by Carld; 11-08-2007 at 09:52 PM.
    It's only ink and paper

  8. #8
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    When I removed my 3 jaw from my L1 nose, presumably for the first time in a zillion years, I had a lot of trouble. I put 2x6s over the bed, put a big high quality prybar between the chuck jaws and bound agains the 2x6s. Put my spanner wrench on the chuck lock collar and couldn't buge it. I ended up with a 8' extension on my spanner and actually rocking the 15x48 lathe onto its feet before the collar finally broke free. The manual said specifically not to put a extension on the spanner, but I didn't have any other choice. I had soaked it in penetrating lube for days. It was to close to seals and the Gamit bearings to risk heat, so it had to be leverage. I nearly had to change my shorts when the collar let loose, it made a huge bang! All is well now though, and the threads are antiseezed...

    Later,
    Jason

  9. #9
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    Be careful on your bashing, that you don't break the back gears or the locking pin.

    First thing I'd try is putting it in backgear and don't pull the locking pin; this ought to lock the spindle against rotation. Arrange to have one of the chuck's key holes on top of the chuck. Insert chuck key, and give it a vigorous yank towards you. If you're lucky, that will be sufficient to start the chuck unscrewing.

    If you're not lucky, more persuasive measures will be needed, and at this point my initial cautionary sentence about being careful not to break something kicks in. I would be careful of doing anything much more forceful and relying on the back gears to lock the spindle. I don't think Atlas gears are known for their strength. Figure out some other way to keep the spindle from turning. One thing you could do, though it would take a bit of preparation, is clamp a couple of pieces of wood together with two bolts, then bore a hole between them on the dividing line just big enough to go around the spindle. Use the boards and bolts to clamp the spindle in place -- you might have to shave a little off the boards' mating surfaces to get clamping to happen. Then stick a bar between the chuck jaws and belt it with a hammer, as somebody else suggested.
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  10. #10
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    Don't use the indexer pin or you may break it or the pulley. I engage the back gear lever, stick the chuck key in one of the pinions and give a yank towards me. Don't put anything in the jaws and hammer. Use a piece of wood across two jaws and tap. Before I'd do that though, I'd use a rod in one of the pinions and hammer. Less chance of breaking out a jaw.

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