6 jaw chuck holds work way off center

Sorry to disseaper for a month I got super busy, finally got to trying to fix this and no matter what I did tightening or loosening the screws it seems like the chuck just wouldn't center.

Decided to take it apart to see how it works and for the life of me I don't understand it. The inserts were numbered with 2 having ball bearings inside and the other two had those slugs. There is no the middle portion that holds in the scroll mechanism for the jaws will not budge but I dont want to absolutely destroy this thing but I do want to get it in better shape if I can. Any insight would be appreciated

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mmcmdl said:
Remove the jaws and re-install them #1 first . The jaws have to installed in order and have to go into the scroll correctly . If that chuck is off .100 something is not correct as a set true can't be thrown off that far .

Take a pic with the jaws fully closed and post it here if you would . ;)

Edit . After looking at the above pic , definately looks like the jaws are installed incorrectly . Looks like the top and top right jaws are out past the OD while the others are not .
Click to expand...
it looks fine.
set tru needs to be adjusted.
you are seeing things Dave...
 
Set-true works pretty much like a 4-jaw chuck. You want to start with two opposing jaws / adjustment screws. While indicating a part that's chucked up, figure out which side is farthest away - loosen that side slightly. Move to the opposite adjustment and tighten it. When tightening, it's best not to really crank down until you're done, just modestly tight. Now repeat those steps until there is very little difference in those two measurements (1-3 thou, you'll get a feel for this). Then switch to the other two adjustment screws and do the same thing. Aim for a closer - perhaps 0.001" or less. Anytime you can't seem to get one pair any closer to zero, switch to the other pair. When everything is dialed in as you like it, snug it all up and recheck. Less than 0.001" should be pretty easy.

It's partially an experience thing. A lot of people avoid 4-jaws because they've cheated themselves out of the experience so it's always hard for them. Those who use a 4-jaw regularly can dial in a 4-jaw, or a set-true, very quickly and to very good precision. Keep at it!

GsT
 
Independant four jaw chucks have been the go-to chucks in my shop for years. After a brief learning curve, I think you'll find they can be zeroed in almost as quickly as a 3 jaw scroll chuck. The big advantages are they can be quickly and easily dialed in to .0005" or less. Most 3 jaw chucks have between .001" and .003" runout. Even the set true varieties aren't necessarily consistent when changing from small to large diameter work pieces or vice versa.

It's much easier to retain consistent diameters with a 4-jaw independent even when the work piece has to be removed and repositioned for another operation.
 
Four jaw lathe chucks indeed are the toughest style chuck and has its' place. I only use them for out of round stock or when the work piece needs to be over tightened. Or when chucking a square sided piece. More times than not I relay on my 10” Six Jaw Gator Chuck on my 16” swing lathe. It'll chuck thin wall stock better than either a three or four jaw chuck without distortion. Having 3” of jaw depth, It will hold the stock true and parallel within less than a .001”. Removing two screws per jaw,the jaws can be reversed. And the accuracy is still right one. Of course the jaws need to be indicated individually when the chuck is first installed on the lathe. Over tightening or out of round stock is the worst enemy of any self centering chuck. But with proper care they will give many years of use..
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Proper proceedure the hole was within a thousand inch out the far end...
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Here's my 4” precision grinding chuck mounted on my cutter grinder. Once again it has 3” of jaw depth for true work piece holding. And will hold the stock within a tenth of being true.
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Grinding OD of valve guide for my 1914 Cadillac
 
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