# Reversing threaded chucks



## rdhem2 (Oct 25, 2013)

Will someone explain to me what the great horror is to reversing a lathe with a threaded chuck spindle.  I have run many lathes, most smaller, with threaded chuck spindles, and all with reverse capabilities.  Even ones in the Navy aboard ship were equipped this way.  If anyone was super safe wouldn't they be?  

I have never had, or seen one come loose.  Hell, half the time, I have to beat hell out of them to get them unscrewed.  

Seems to me, when and where I read this, that it is a newby machinist tale.  

Billie-Bob said so.  Must be true.:nuts:


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## Bill C. (Oct 25, 2013)

rdhem2 said:


> Will someone explain to me what the great horror is to reversing a lathe with a threaded chuck spindle.  I have run many lathes, most smaller, with threaded chuck spindles, and all with reverse capabilities.  Even ones in the Navy aboard ship were equipped this way.  If anyone was super safe wouldn't they be?
> 
> I have never had, or seen one come loose.  Hell, half the time, I have to beat hell out of them to get them unscrewed.
> 
> ...



I agree most of the time they are a bear to get off.  But there is a chance that some of the new machinists don't snap their chucks on tight enough.  In that case the chuck could loosen and mess up a work piece.  Also I feel it depends on the spindle speed when throwing the lathe in quick reverse.  Probably why some manufactures use cam lock or bolt on methods to attach their chucks.


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## pdentrem (Oct 25, 2013)

Just a small historical point. All lathes in the past had threaded spindles until, someone around the 1930s invented Camlocks like L0 series or D1 etc. 
Pierre


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## Dave Smith (Oct 25, 2013)

Russ---the reason chucks get so tight is because there is constant torque when running in forward--when you run in reverse there is still torque but nothing to keep it from tightening--it just wants to unscrew. it only takes one time of unscrewing to cause a lot of havoc. it's not worth the problems by using reverse very much--using collets would be better for reverse turning---Dave  :thinking:


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## benmychree (Oct 26, 2013)

I, too have very little trouble with chucks unscrewing if reversed while running; as others have observed, if the chuck is snapped up against the shoulder smartly, the very rarely come off; when it has happened I just turn off the switch or momentarily hit forward rotation, and it threads back on; I've been at this for very nearly 50 years now.


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## rdhem2 (Oct 26, 2013)

Hey Guys, thanks for the input and I totally agree with you all.  However the horror stories, probably never witnessed personally, are repeated time after time.  I was taught, and have the habit of, allowing the spindle to stop before reversing.  One reason I guess is a lot of the machines I have operated were single phase so flipping the reverse switch has no effect at all unless you allow the starting switch in the motor to close to go in reverse.  And you have to stop or all but stop for them to do that.

Keep sweeping the _*SWARF*_ out the door!


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