G0752 Chuck stuck good and hard!

SLK001 said:
1) Lock your spindle.
2) Mount some kind of steel bar in the jaws horizontally (you won't operate your lathe).
3) With the bar sticking out, hang weights from the bar - as much as it will hold.
4) Walk away (however, protect the ways from a bar coming down).

Overnight, your chuck should break loose.
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I've used this method on a hundred year old Seneca Falls and it worked within a couple hours of setting it up.
I did have a goodly amount of PB Blaster on the spindle thread area from previous attempts.
 
People are surprised on the amount of torque that it applies. Fifty pounds on the end of a 3 foot bar gives a moment arm of 150 ft-lbs - a 4 foot bar gives 200 ft-lbs. And this method doesn't impart any shock to the lathe.
 
Thanks for the comments, folks. I left the spindle swimming in penetrating oil for several days, then I went back out and tried the suggested methods of removing the chuck.

Alas, it is stuck. As in, stuck. I really can’t get it loose with one hand on the spindle and one hand on the chuck - I need to have the spindle locked good and solid so I can work on the chuck with both hands. Unfortunately, this lathe does not have a spindle lock, but thanks for suggesting that. Also, I don’t have a machine shop - this lathe is the only such machine I have, as I’m set up almost wholly for woodworking, so I can’t readily fabricate metal tools. Otherwise I’d make an adjustable wrench with three nubs that could clamp down completely around the spindle. That would immobile the spindle but good!

As it is, I’m resigned to taking apart the spindle assembly so I can remove the spindle and chuck from the lathe. Then I can put the spindle in a padded vise and have both hands free for the chuck. I have an exploded diagram of the spindle assembly, but I would appreciate any tips on the disassembly and re-assembly process. I understand there‘s a potential issue with reinstalling the bearings, and there’s a key on a shaft somewhere? I can just picture myself cussing as I hear an unseen something fall off inside the housing…
 
Perplexed said:
As it is, I’m resigned to taking apart the spindle assembly so I can remove the spindle and chuck from the lathe. Then I can put the spindle in a padded vise and have both hands free for the chuck. I have an exploded diagram of the spindle assembly, but I would appreciate any tips on the disassembly and re-assembly process. I understand there‘s a potential issue with reinstalling the bearings, and there’s a key on a shaft somewhere? I can just picture myself cussing as I hear an unseen something fall off inside the housing…
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Don't resort to dismantling anything just yet. Open the gearbox and stick something like nylon, or some other hard plastic into the gearing so that the spindle can't move forward. Once your spindle is immobilized, you can try the "weight on a stick" approach. Removing the spindle would be the LAST thing that I would do (okay, second from the last - the last thing I would do would be to turn the chuck mount off the spindle).
 
As already mentioned, don't dismantle anything yet.
Can you unbolt the chuck from the backing plate? Cut these bolts off if you have to. If you can separate them, you can heat the backing plate up and thermocycle it to break the bond holding it to the spindle.
 
And dont jam anything in the gears unless you really want damage.
 
This lathe doesn't have a gear box. furthermore, the external gears driving the change gears are nylon so I would strongly advise trying to gain leverage by jamming the gears. It's not even a good idea with steel or cast iron gears.

You will not be able to break the chuck loose by use of your hands. I measured the torque required to break the chuck loose on my 602 at 35 lb-ft. Once it is broken free, then you can spin it off by hand.
 
For my Jet 1024, which also has a screw on chuck, I've used the method described by Grizzly for the G9249 (Grizzly's version). It involves mounting a bar in the chuck perpendicular to the face and hitting it with a dead blow hammer. As unnerving as appears, any impact would be tangent to the spindle bearing, and I've never needed to hit very hard.
 

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Is it possible to make a split clamp wrench out of some beefy aluminum plate and clamp around where the pulleys are? You can put quite a bit of force on it with such a wrench, and you can make it with the lathe, as long as the stuck chuck can hold the plate.
 
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