3 jaw chuck with 2 piece (reversible) jaws

taiwanluthiers

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I finally bought a 3 jaw chuck, got 8 inch instead of 10 inch I was originally going to get. Cheaper in both price and shipping, and the lathe seems to run smoother with lighter loads.

The chuck I got has reversible 2 piece jaws. They're more expensive than normal 3 jaw chuck with one piece jaws (that has to include a reverse jaw as well). Is there a reason for this? I only got it because I like the idea of being able to unbolt and reverse the jaws, and also making soft jaws for it. Is there any advantage for having bolt on jaws rather than one piece jaws?

I did have to machine the back plate because the outer bolt holes on my spindle only has 4 holes, and I had to drill extra holes onto the back plate...
 

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I have both types of jaws, I never noticed a difference in accuracy between them. The 1 piece may be a little easier to change as you only need the chuck key. The 2 piece do have the advantage of easily making soft jaws.
 
So one question... is there any advantage to having a bigger chuck on a lathe? On my victor lathe a 8 inch chuck seems to fit the lathe well, as in it just about fills the footprint of the bearing. What's the rule of thumb for chuck size?
 
Use the smallest chuck that will safely get the job done. This is primarily to save wear on your spindle bearings.
So I just looked at Abom's videos on his victor lathe, and he seems to be spinning 10" six jaw chucks on it. I read elsewhere that for scroll chucks the rule of thumb is half the lathe's swing.

So why would Abom want to spin a 10" chuck on a victor lathe? 8" seems to fit the lathe very well and the lathe runs smoother as a result too.
 
Well, you can run chucks as large as your lathe can take but why would you do that unless you need the capacity? You have to remember that the spindle is seeing the weight of the chuck, the weight of the work piece, the extension of the chuck and workholding position from the face of the spindle register and the cutting forces as you cut the work. Just as a general rule, keeping things as light as possible and as close to the spindle as possible makes sense.

CAN you run a bigger chuck? Sure, run what you have or what you like but you asked for a rule of thumb ...
 
Well, you can run chucks as large as your lathe can take but why would you do that unless you need the capacity? You have to remember that the spindle is seeing the weight of the chuck, the weight of the work piece, the extension of the chuck and workholding position from the face of the spindle register and the cutting forces as you cut the work. Just as a general rule, keeping things as light as possible and as close to the spindle as possible makes sense.

CAN you run a bigger chuck? Sure, run what you have or what you like but you asked for a rule of thumb ...
Yea I get that. Plus bigger chucks have a minimum size too, not to mention being heavy as hell. My variant of Victor lathe does not have a D1-6 chuck mount so that means I must bolt/unbolt the chuck onto the lathe. Often this means unbolting it from the back plate, then the back plate from the spindle. It would be a pain if the chuck weighted more. 8" chuck is a comfortable size to handle, anymore and it becomes difficult.

Now I need to figure out how to true the chuck a bit, because it's giving me a 0.1mm runout.
 
For all first operations work like a 3 jaw is intended for, the chuck will be precisely accurate and run out is not an issue. Once you turn the work and must re-chuck it then that becomes a second operation, the province of a 4jaw independent or some other kind of adjustable chuck.
 
My first choice would always be a 2 piece jaw set up. And the smallest size that fits the work type that you do. With a 2 piece jaw you have the options of boring soft jaws (mandatory in my case) or using pie jaws . It’s easy to bore soft jaws to hold a disk 3 inch dia x 1/8 wide and hold it flat and true in the jaws. Also easy to turn jaws to a 1/2 inch dia x 1/8 depth and hold on the Id of a washer. I have had times when I moved chuck to the mill and bored soft jaws excentric for turning cams after returning chuck to the lathe.
jimsehr
 
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