Threaded chuck is stuck

michieltje

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So my 3 jaw chuck (Plate)is stuck onto the threads, any advice on how to get it loose?
I've tried heating from the outside and cooling inside but no succes yet.
It is an older lathe with a threaded spindle nose, no tapers or anyting like that.
 

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I would avoid heat - you don't want to warp the spindle at all. I'd take the spindle out and soak it in a penetrant before using heat. A simple and good penetrating oil can be made using acetone and ATF fluid (1:1 ratio, and it does not have a good shelf-life).

If you can lock the spindle from rotating without using back gears, you can get away with this next method. A lot of people put the spindle in "back gears" while keeping the non-back gears engaged - this effectively stops it from turning, and is a bad idea because of the potential to break teeth off of your spindle or back gears). Take a piece of stock and bolt it to the chuck back plate. Centering the stock is not essential, nor is the material (e.g. a piece of 2x4 works just as well). Then, with a good sized hammer, knock the wood in a counter clockwise rotation (front side goes down). It may take a couple of good whacks, but once it starts to move, you should be able to do it by hand.
 
I bought a lathe one time that I just fixed up to sell and that had a 3 jaw chuck on it that was stuck. I cut the end off a larger size allen wrench and chucked it up in the 3 jaw chuck. Used an impact wrench on the allen wrench piece and after a few whacks it came free. The sudden jar can break things free.

I suggest you do NOT use the back gears to hold the spindle from turning. You can easily break teeth off the gears.

Use penetrating oil though. That can help as well.

Ted
 
Good luck. I've got a 26 inch chuck stuck on a spindle I've been trying to get off for months. Hopefully when I get it where I can power it I can pop it off.
 
I think that it is generally safe to use the back gears to remove chucks, if shock is not used, of course it would depend on how robust the lathe may be, such as the materials used in the gear train. generally, I think the problem lies in the fact that the chuck threads force the backplate against the shoulder of the spindle, not sticking of the threads themselves, thus, penetrating oil is not going to be much help; I would cut a piece of wood to fit between the chuck jaw and the rear way of the bed, and in back gear, pull the belt by hand to try to unscrew the chuck, repeatedly trying to break it loose. On larger lathes of industrial size, this can be done under power.
 
Good luck. I've got a 26 inch chuck stuck on a spindle I've been trying to get off for months. Hopefully when I get it where I can power it I can pop it off.
I had to remove a chuck from the spindle of a 36" swing Nebel lathe over 50 years ago, I spit a number of 4 x 4s trying to get it off, to no avail, I finally used a 4"square boring bar between the chuck jaws (4 jaw) down in between the ways, in the lowest speed, and bumped reverse repeatedly with a 30 HP motor, direct connected; after many repeated attempts, it finally came off without damage, it was not corrosion or crud, it was just years of heavy interrupted cuts that hammered the chuck against the spindle shoulder. The lathe was a POS, poorly designed and made and taken care of, finest feed was something over 1/64".
 
So i tried to run the lathe like this and i tried a 6 foot cheaterbar on the faceplate with no succes. Im lifting the 3000 pound lathe with it. Anyone have more ideas?
 

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So i tried to run the lathe like this and i tried a 6 foot cheaterbar on the faceplate with no succes. Im lifting the 3000 pound lathe with it. Anyone have more ideas?
Wait... if the spindle is reverse threaded (as I expect it is...) and you're lifting the lathe in this configuration then it seems to me that you're further tightening the chuck.
I had a 5" chuck well stuck on my South Bend and I had to spin the chuck backwards to break it loose.
 
I bought a lathe one time that I just fixed up to sell and that had a 3 jaw chuck on it that was stuck. I cut the end off a larger size allen wrench and chucked it up in the 3 jaw chuck. Used an impact wrench on the allen wrench piece and after a few whacks it came free. The sudden jar can break things free.

I suggest you do NOT use the back gears to hold the spindle from turning. You can easily break teeth off the gears.

Use penetrating oil though. That can help as well.

Ted
I'll try this tomorrow but i done have high holes as the 6 foot cheater bar didnt work..
 
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