# Chuck help



## emasbury (Jun 29, 2014)

Hey Folks, I have a Craftsman/Atlas 12 X 36, the stand alone model, which has a 5 inch 3 jaw chuck that needs some serious help. I have decided to replace the chuck. My questions are as follows: I want a larger chuck, what is the largest size I can put one the lathe, 6 inch, 8 inch or larger? I'm going to be turning some soft stuff so should I get a 6 jaw chuck in whatever size I decide on, or just stay with the 3 jaw? Looking forward to your help and advice. So thanks in advance and I greatly appreciate any and all help you folks pass my way, Ed, Eagle River, Alaska.


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## Pat of TN (Jun 29, 2014)

Looking through my Grizzly catalogue, it seems their (and a lot of other) 12" swing lathes come with 6" three-jaw and 8" four-jaw chucks. I would say either size would work, six or eight inches. What determines this is how far out the jaws can go before they hit the ways. On a 12" swing lathe, with an 8" chuck, the jaws would have to be out of the chuck by about two inches or more, theoretically, so I would say an eight-inch chuck would suffice, but no larger.I would also recommend you look into getting a four-jaw, independent chuck over a three-jaw scroll/universal chuck. A brand-new, quality three-jaw chuck can maybe repeat to a few thousandths' runout (.003 to .005 ish). Although a four-jaw does take more time since you must dial the part in to run true, the accuracy and TIR are limited only to the accuracy of your indicator and the time you wish to spend on it. A four-jaw chuck can also hold odd-shaped (IE square, octagon) pieces. Then again, you can adjust the runout of a three-jaw somewhat with a mallet and an indicator. If all you need is .005 TIR (or, runout that you can't see at a glance), a three-jaw is fine.I would also advise against a six-jaw chuck. A six-jaw chuck looks like a mean device, but they really don't provide a great difference in precision. They also require good, truly round stock to function well. If you work with a lot of tubing or pipe, a six jaw chuck also comes in handy due to the greater distribution of force.Sorry for the long-winded response, but there's a lot to choosing a chuck. Summary: I'd try an eight-inch chuck. A four-jaw independent chuck if you want or need the ability to turn square stock and/or less than .005 runout, or a three-jaw scroll chuck if you don't need sub-.005 runout and only mess with round stock...


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## emasbury (Jun 29, 2014)

Pat of TN said:


> Looking through my Grizzly catalogue, it seems their (and a lot of other) 12" swing lathes come with 6" three-jaw and 8" four-jaw chucks. I would say either size would work, six or eight inches. What determines this is how far out the jaws can go before they hit the ways. On a 12" swing lathe, with an 8" chuck, the jaws would have to be out of the chuck by about two inches or more, theoretically, so I would say an eight-inch chuck would suffice, but no larger.I would also recommend you look into getting a four-jaw, independent chuck over a three-jaw scroll/universal chuck. A brand-new, quality three-jaw chuck can maybe repeat to a few thousandths' runout (.003 to .005 ish). Although a four-jaw does take more time since you must dial the part in to run true, the accuracy and TIR are limited only to the accuracy of your indicator and the time you wish to spend on it. A four-jaw chuck can also hold odd-shaped (IE square, octagon) pieces. Then again, you can adjust the runout of a three-jaw somewhat with a mallet and an indicator. If all you need is .005 TIR (or, runout that you can't see at a glance), a three-jaw is fine.I would also advise against a six-jaw chuck. A six-jaw chuck looks like a mean device, but they really don't provide a great difference in precision. They also require good, truly round stock to function well. If you work with a lot of tubing or pipe, a six jaw chuck also comes in handy due to the greater distribution of force.Sorry for the long-winded response, but there's a lot to choosing a chuck. Summary: I'd try an eight-inch chuck. A four-jaw independent chuck if you want or need the ability to turn square stock and/or less than .005 runout, or a three-jaw scroll chuck if you don't need sub-.005 runout and only mess with round stock...



Pat , Thanks for you advice, I was leaning toward the 8 inch 3 jaw and you pushed me over the edge. As for the 4 jaw I already have a fairly good one the serves me well.  Thanks Again, Ed


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## Ulma Doctor (Jun 29, 2014)

bigger is not always better,
most chucks have reverseable jaws for when you do larger diameter work.
you really don't wan't to put any more added weight to the spindle than is necessary.
but a 4 jaw chuck of even questionable quality can be dialed in, it may take more time to set up than a 3 jaw but you can get dead nutz


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## Pat of TN (Jun 29, 2014)

emasbury said:


> Pat , Thanks for you advice, I was leaning toward the 8 inch 3 jaw and you pushed me over the edge. As for the 4 jaw I already have a fairly good one the serves me well.  Thanks Again, Ed



Absolutely. Glad you have a four-jaw, to me a four-jaw independent should (almost) always be the first choice over a three-jaw scroll or even a collet chuck. Unfortunately my little 6x18 Craftsman only came with a three-jaw that's as old as the lathe is (at the least the mid-50s). Trust me, I share your agony in having a worn-out scroll chuck!

Ulma Doctor does bring up a good point, I might add. What I recommend is, purchase your chuck from a reputable company (assuming you buy new) and if you notice anything wrong or amiss, ask to return it. What I mean by 'wrong' is what I mentioned before, the jaws getting close to the ways when opened up somewhat, on top of Ulma Doctor's note about weight on the spindle. This would mainly become clear in the form of a more sluggish start-up; there may be other things as well but I can't think of any offhand.

One more thing - if you can, get a chuck with two-piece jaws. If you don't know, a two-piece jaw has a master jaw that rides the scroll and a top jaw that grips the part that is held on to the master jaw by cap screws. You can simply reverse these top jaws for holding large-diameter pieces rather than having a second set of jaws, and it also opens up a whole new world of workholding - soft jaws.


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## emasbury (Jun 29, 2014)

Pat of TN said:


> Absolutely. Glad you have a four-jaw, to me a four-jaw independent should (almost) always be the first choice over a three-jaw scroll or even a collet chuck. Unfortunately my little 6x18 Craftsman only came with a three-jaw that's as old as the lathe is (at the least the mid-50s). Trust me, I share your agony in having a worn-out scroll chuck!
> 
> Ulma Doctor does bring up a good point, I might add. What I recommend is, purchase your chuck from a reputable company (assuming you buy new) and if you notice anything wrong or amiss, ask to return it. What I mean by 'wrong' is what I mentioned before, the jaws getting close to the ways when opened up somewhat, on top of Ulma Doctor's note about weight on the spindle. This would mainly become clear in the form of a more sluggish start-up; there may be other things as well but I can't think of any offhand.
> 
> One more thing - if you can, get a chuck with two-piece jaws. If you don't know, a two-piece jaw has a master jaw that rides the scroll and a top jaw that grips the part that is held on to the master jaw by cap screws. You can simply reverse these top jaws for holding large-diameter pieces rather than having a second set of jaws, and it also opens up a whole new world of workholding - soft jaws.




We must have the same old 3 jaw, mine has seen better days, can't wait to get a new chuck.  Thanks guys.


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## kd4gij (Jun 29, 2014)

Here is my lathe with an 8" chuck it serves me well.



I needed the 6" 4jaw for a quick project and was to lazy to change it :lmao:


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## emasbury (Jun 30, 2014)

kd4gij said:


> Here is my lathe with an 8" chuck it serves me well.
> View attachment 79457
> 
> 
> I needed the 6" 4jaw for a quick project and was to lazy to change it :lmao:




Now that would be something I would do.


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## wa5cab (Jun 30, 2014)

Ed,

For relatively soft stock up to about 1" diameter, I would use collets (except for wood I would use centers).  Above that you are stuck with chucks (unless you want to spend really big bucks).  If you do a lot of the same diameters, a 6" 3-Jaw with two piece jaws and soft jaws might be a good choice.  You can bore the bearing faces of the soft jaws to significantly spread out the clamping area.  Just remember that you have to properly load the jaws outward (if gripping the OD of the workpiece) before you bore them.

Robert D.


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## Mondo (Jul 7, 2014)

kd4gij said:


> Here is my lathe with an 8" chuck it serves me well.
> View attachment 79457
> 
> 
> I needed the 6" 4jaw for a quick project and was to lazy to change it :lmao:



My, you ARE lazy!   The problem with this is you cannot gain the major advantage oif the 4-jaw over the three-jaw, being the ability to center the work dead-on.  The setup you have pictured will suffer from any TIR of the three-jaw no matter what you do to center the work  in the four-jaw.  A lazy setup, yes, brilliant, no.  :nuts:
Really now, how difficult is it to thread the 3-jaw off and thread the 4-jaw on???

- - - Updated - - -

To answer the original question of how big a chuck will fit, the answer is in how big a chuck is practical.   An 8 inch diameter chuck is the limit of practicality on these lathes, be it a 3-jaw, 4-jaw, or 6-jaw.  Anything bigger than 8" in diamater will be grossly excessive.  

A 10" diameter 3-jaw chuck with an appropriate backplate will weigh about 60 to 80 lbs and will be gripping the work several inches out from the end of the spindle.  This will amplify any TIR in the system and will detract from the accuracy oif the lathe.


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## rafe (Jul 7, 2014)

I've done that too and not out of laziness but out of necessity.I had a 3 jaw for my SB but no 4 jaw at that time, however I did have a 4 jaw off of a small atlas that I made a threaded shaft for and it worked perfectly for what I needed to do on more than one occasion , I have since gained a nice 4jaw and it usually stays on until I have to use the 3 jaw ...well not have to prefer to


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## Walt (Jul 8, 2014)

Spiral_Chips;213471  The setup you have pictured will suffer from any TIR of the three-jaw no matter what you do to center the work  in the four-jaw.
[/QUOTE said:
			
		

> Are you sure of that?
> 
> I'm have no actual experience to draw on, but if what you are saying is true, how can a 4-jaw chuck be used to compensate for runout in the first place?


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## kd4gij (Jul 8, 2014)

Spiral_Chips said:


> My, you ARE lazy!   The problem with this is you cannot gain the major advantage oif the 4-jaw over the three-jaw, being the ability to center the work dead-on.  The setup you have pictured will suffer from any TIR of the three-jaw no matter what you do to center the work  in the four-jaw.  A lazy setup, yes, brilliant, no.  :nuts:
> Really now, how difficult is it to thread the 3-jaw off and thread the 4-jaw on???
> 
> - - - Updated - - -
> ...




    The abor the 4 jaw is on was made in that 3 jaw. It is stamped for jaw 1. The runnout on the 4 Jaw is less than .001. The job at hand was a 2min job bore a 1 1/8 off center hole to 1 1/4"  for the boring bar you see in the pic. For bigger jobs the 4 jaw gets screwed on the spindle. That 8" 3 jaw is to havey to take off for what I was doing at the time. Works for me.


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## wa5cab (Jul 12, 2014)

OK.  Makes more sense, now.

On the root issue (chuck weight), do you have a way in which to hold the 8" chuck when you install or remove it?  If not, and if the chuck weighs too much for you to comfortably support with one hand as you remove it but not too much for you to pick up and carry (NOTE: in the latter case, the chuck is too heavy for the spindle of an Atlas), here's a cheap and dirty solution.

Get a piece of 4X4 wood (treated fence post works well) and cut it about 4" to 5" longer than the width of the ways.  Run the chuck jaws into the center and out of the way.  Place the 4X4 on the ways and center it up front-to-back.  Slide it up against the face of the chuck, hold it there firmly with the right hand, and with the left hand and a pencil scribe the arc of the OD of the back of the chuck body onto the side of the 4X4.  Cut the arc out with your bandsaw and clean it up a little with sand paper.  Place the 4X4 on the ways and slide it under the chuck.  If too tight, thin the 4X4 a little with your belt sander.  

To use, slide the 4X4 under the chuck and unscrew the chuck until it is clear of the spindle.  Slide the 4X4 a little way down the ways and then lift it and the chuck using both hands.  Hold it against your chest so that you don't dump the chuck onto your toes as you walk.  To reinstall the chuck, reverse the process.  A good application of paste wax on the arc in the block will help keep oil from soaking the top of it but not rub off onto the chuck during use as paint would.  Same for the bottom that slides on the ways.  You can paint the sides and ends.  If you want to get fancy, cut about 2-1/2" height out of the part of the bottom that doesn't slide on the ways.  That will reduce the top-heavy problem when carrying and reduce finger-pinch probability.

Robert D.


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## kd4gij (Jul 13, 2014)

Thanks Robert

 I do have a cradle like that to help when changing the chuck. For a quick simple job the 4 jaw works just fine as in the pic. It does get mounted on the spindle for real work. I was just enlarging a  offcentered hole on a rectangle block witch is theboreing barr holder for mmy qctp. took all of 2 min. not worth swaping chucks twice for. Just another way to skin a cat.

  I didn't mean to hijack the op's thread. Just posted the pic to show that an 8" chuck works fine on the 12" atlas craftsman lathe. Chose that pic becouse it showes the size deffernce between 6" and 8" chuck.


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## wa5cab (Jul 14, 2014)

That makes sense.

RD


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## Andre (Jul 14, 2014)

By the way, I recommend a 4 jaw scroll chuck. More gripping area than a 3 jaw and you can grip square stock. And I know what your thinking......but you can grip hex in a 4 jaw!


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