# Tight 3 jaw chuck?



## cdhknives (May 5, 2013)

My 3 jaw chuck has gotten really tight.  It takes significant effort to twist the key.  I'm assuming I have gotten some debris in there and need to take the chuck apart and clean it.  I've already tried to flush it with copious amounts of oil and WD-40 with no change.

Any tricks or pitfalls I should be aware of?  This is a Union Manufacturing Co chuck on my Atlas QC-54.


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## Dr.Fiero (May 5, 2013)

Make note of the number markings on the jaws vs. what's marked on the chuck!!

Chances are, unless you crashed the chuck, there's just gunk inside.
Resist the urge to use grease on assembly (aka crap catcher).


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## pdentrem (May 5, 2013)

Not much to them, no springs and clips that come flying out. I believe there used to be a topic here showing this. Have to search for it.

There is a couple YouTube videos by Halligan142 showing how. 
Pierre


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## Ray C (May 5, 2013)

Also resist the urge to take a file to it other than removal of obvious manufacturing burrs.  There will come a time when when it's as loose as a goose and the jaws won't be as predictable.  Enjoy the snug fit as long as you can.


Ray


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## cdhknives (May 5, 2013)

Thanks!

The screws all came out with a reasonable amount of pressure.  The 2 halves didn't want to come apart though...I put the 6 back screws in part way, so the heads were sticking about halfway out, and repeatedly dropped it on the floor from 2-3" up to drive the halves apart.  I now have a 1/8" gap and no more thread in the screws to work with.  Time to worry it apart the rest of the way...without adding burrs to that fine gapless seam!

It's original to the lathe AFAIK, so I'm not worried about manufacturing burrs.  It would be 60+ years old.  I do wonder about steel wool fragments from my cleanup cycle when I got it.  It was pretty gunky and ugly from 20+ years of neglect!


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## Ray C (May 5, 2013)

I could only hope my joints are still tight when I'm 60+ years old.  53 so far and the prognosis is not too good  :angry:




cdhknives said:


> Thanks!
> 
> The screws all came out with a reasonable amount of pressure.  The 2 halves didn't want to come apart though...I put the 6 back screws in part way, so the heads were sticking about halfway out, and repeatedly dropped it on the floor from 2-3" up to drive the halves apart.  I now have a 1/8" gap and no more thread in the screws to work with.  Time to worry it apart the rest of the way...without adding burrs to that fine gapless seam!
> 
> It's original to the lathe AFAIK, so I'm not worried about manufacturing burrs.  It would be 60+ years old.  I do wonder about steel wool fragments from my cleanup cycle when I got it.  It was pretty gunky and ugly from 20+ years of neglect!


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## cdhknives (May 5, 2013)

Well it's apart and back together.  Other than a possible burr (from being dropped???) on the corner of one track, nothing obvious was found.

I polished the jaws using the poor boy lap (slab of granite and 240 grit wet/dry carbide sandpaper) and it is a little better.  Now it mainly binds in the middle 1/3 of travel instead of 2/3 of travel.

I tried using a black sharpie to mark up the contact surfaces to check for rub points.  That did't narrow it down much.  It seems tight all over.

...and yes I was putting the #1 jaw in the groove with #1 stamped next to it, #2 in #2, and #3 in #3.  I have to get back to work Monday, so it may be a couple of days until I can mess with it again.


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## Ray C (May 6, 2013)

You know, you could have a slight issue with the scroll interacting with the teeth/threads on backs of the jaws.  Over tightening a chuck is how the damage typically occurs.  I'm not sure what gives-way; the scroll or the teeth.  You might want to try slathering with markup dye and see where things are rubbing.


Ray




cdhknives said:


> Well it's apart and back together. Other than a possible burr (from being dropped???) on the corner of one track, nothing obvious was found.
> 
> I polished the jaws using the poor boy lap (slab of granite and 240 grit wet/dry carbide sandpaper) and it is a little better. Now it mainly binds in the middle 1/3 of travel instead of 2/3 of travel.
> 
> ...


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## wa5cab (May 7, 2013)

Crank all of the jaws out and then try them one at a time.  Also, while you had it apart and the scroll out, did you try sliding each jaw down its track?

Robert D.


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## cdhknives (May 7, 2013)

wa5cab said:


> Crank all of the jaws out and then try them one at a time.  Also, while you had it apart and the scroll out, did you try sliding each jaw down its track?
> 
> Robert D.



Yes.  That's how I discovered that only 2 jaws are tight and after some polishing of the jaws only in the middle third of travel.  The scroll+chuck spins freely with the jaws removed.  I'm thinking I'll try some 600 grit on the tracks at the tight points.  The second set of jaws is similarly tight at the same places.


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## wa5cab (May 7, 2013)

Before you do any sanding on the slots, I would try each jaw one at a time in the other two tracks.  And see whether the tightness goes with the jaws or stays with the tracks.  

Robert D.


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