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  1. #1
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    Default Draw tube STUCK!

    Hey guys,

    Had an issue with my new to me Mazak MP630 chuck not actuating - long story short the issue is a stuck draw tube (probably due to a life of cast iron machining)

    I've managed (after a LOT of swearing and anger) to remove both the chuck and the actuator, so all that is now left is the draw tube up inside the spindle.




    I made a plate to bolt the the spindle nose to push against the draw tube, in the hopes that i could make it move, but instead all i did was dish a piece of 12mm 250gr steel.




    Any tips at this stage?

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    If you are imparting that amount of force on it, you will likely have better luck pulling it than pushing it.

    Work from whichever end has a male thread exposed, screwcut a nut that can be jacked against the end of the spindle.

    Most likely it is rusted in from condensation, there is really no way for chips or dust to get inside there when there's a chuck mounted.

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    Its already chucked in the lathe. Bore it out.

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    Quote Originally Posted by gbent View Post
    Its already chucked in the lathe. Bore it out.
    Aside from the need to replace it afterwards, if op is lucky enough that it is seized close to the spindle nose then that can work.

    Otherwise, it's easier said than done. On a typical lathe the drawbar will be upwards of three feet long, with nothing to mount an outboard support to. A quick google tells me the spindle bore is 3.46" on that machine, wall thickness of the drawtube .205", and the Z axis stroke 23.8".

    Unless it has sat unused for a long time, it's probably not that badly stuck. I'd persevere with trying to remove it for a while yet before resorting to more drastic measures.

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    Quote Originally Posted by gregormarwick View Post
    Aside from the need to replace it afterwards, if op is lucky enough that it is seized close to the spindle nose then that can work.

    Otherwise, it's easier said than done. On a typical lathe the drawbar will be upwards of three feet long, with nothing to mount an outboard support to. A quick google tells me the spindle bore is 3.46" on that machine, wall thickness of the drawtube .205", and the Z axis stroke 23.8".

    Unless it has sat unused for a long time, it's probably not that badly stuck. I'd persevere with trying to remove it for a while yet before resorting to more drastic measures.
    My thoughts exactly.

    Sent from my G8141 using Tapatalk

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    Did you turn the hydraulic pressure on the chuck all the way up before removing the cylinder? I'm guessing on a lathe that size there is lot of push on that cylinder.

    If you have already done this step, you don't have much left of non-lethal means.

    On a 3 1/2" bore, expect at least 10 tons per inch of diameter of force required. Stuck hard or long engagements may require over 20 tons/inch. A lathe spindle is one place where a bigger hammer isn't your friend.

    As far as length of bore, yes, it will be a problem for an operator. A machinist, not so much.

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    Quote Originally Posted by gbent View Post
    Did you turn the hydraulic pressure on the chuck all the way up before removing the cylinder? I'm guessing on a lathe that size there is lot of push on that cylinder.

    If you have already done this step, you don't have much left of non-lethal means.

    On a 3 1/2" bore, expect at least 10 tons per inch of diameter of force required. Stuck hard or long engagements may require over 20 tons/inch. A lathe spindle is one place where a bigger hammer isn't your friend.

    As far as length of bore, yes, it will be a problem for an operator. A machinist, not so much.
    Yeah I tried cranking the pressure and got basically nothing out of it.

    I'll see how I go tomorrow before I resort to anything drastic.

    Sent from my G8141 using Tapatalk

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    Quote Originally Posted by gbent View Post
    Did you turn the hydraulic pressure on the chuck all the way up before removing the cylinder? I'm guessing on a lathe that size there is lot of push on that cylinder.

    If you have already done this step, you don't have much left of non-lethal means.

    On a 3 1/2" bore, expect at least 10 tons per inch of diameter of force required. Stuck hard or long engagements may require over 20 tons/inch. A lathe spindle is one place where a bigger hammer isn't your friend.

    As far as length of bore, yes, it will be a problem for an operator. A machinist, not so much.
    Chuck actuators don't generate particularly large forces. Low pressure hydraulics and fairly small pressure area. On a machine that size it will be in the range of ~30KN. Not enough to budge even a lightly stuck tube.

    Drawtubes are also not normally a particularly tight fit in the spindle bore, so unless it's really rusty it seems unlikely to be stuck too badly.

    A plug/cap screwcut to fit the outer end of the drawtube, hire a hollow cylinder, pull it out.

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    Dam up one end. Apply pressure. Pour in liquid N. If you can't get it try dry ice and pour in ethanol. If that doesnt blow a torch through it for awhile. Repeat. Still risk involved.

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    Chuck actuators don't put out high tonnage forces. They'd rip everything apart and distort the spindle if they did.

    I would turn up an adapter to fit a hollow enerpac cylinder. I have a 30 ton hollow ram I use for rebuilding rolls a lot and I haven't found anything under 7" it won't pull apart.

    Just make everything tight fitting and concentric. Pulling forces aren't very effective if they are crooked.

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    Use an expanding collet (you might need to make it) that fits the id of the tube, connect a piece of all thread that goes clear through the spindle, alternate pulling from each end until you get some clearance.

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    With all due respect to the other poster's experience, I'd still bore it out if about 20 tons won't move it.

    I have the equipment to horse out most things. But I have found once I get past about 10 tons per inch of diameter the risk of damaging one or the other parts increases quiet rapidly. I have had parts with rust and dirt between the mating components split the outer sleeve, which had about a 3/16 wall on a 2" diameter. If its a field repair, I use more tonnage. If its in the shop and fits on a machine, I look at which part is the more difficult to replace and try hard not to damage that part.

    If you only get part of the tube bored out before it loosens, you can thread the tube and add an extension.

    If you bore out the tube, you know the damages. You replace the tube, which is not a difficult or costly process. On the other hand if you damage the spindle, for all practical purposes you have scrapped the lathe.

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    To add to gbent's comment- its probably crapped up at the chuck end from swarf and coolant rather than from the actuator end, so the chances of boring out that end will allow you to get the rest of it out of the spindle with much less effort. I would certainly try what Garwood suggested 1st - pulling against the end of the spindle would seem the way to proceed then going to a more destructive approach if that does not work. A a friend often says - "things hate people".

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    there is a gap between tube and spindle i.d.
    you can slow but sure pick the rusted fines out and save the whole thing
    I've done it
    it sucks

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    Sigh... I've caved in... At least I can get 75*90 honed hydraulic cylinder, so making a new draw tube should be relatively straight forward (put a thread on each end and celebrate)

    Sent from my G8141 using Tapatalk

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    Quote Originally Posted by xa-mont View Post
    Sigh... I've caved in... At least I can get 75*90 honed hydraulic cylinder, so making a new draw tube should be relatively straight forward (put a thread on each end and celebrate)

    Sent from my G8141 using Tapatalk
    Did you try to pull it out with a hollow ram?

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    Quote Originally Posted by gregormarwick View Post
    Did you try to pull it out with a hollow ram?
    Couldn't find one locally sadly (I live in a rural City in Victoria, Australia)

    Sent from my G8141 using Tapatalk

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    might be too late but had something similar when a cooling channel got plugged on a integral motor machine and had to pull the stator. All thread was mentioned, but I used hollow hydraulic jack to pull it out, wasn't to clear if that was suggested or not

    stat1.jpgstat2.jpgstat3.jpg

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    So I ended up boring it basically all the way out. I'm now back up and running with a new draw tube.... What a shit job that was!

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    all the way?? how the hell did it bind up all the way? happy to hear back up!


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