4 Jaw Chuck

It looks like a Bison 6 jaw Set-Tru chuck to me.
I was under the impression that the chuck is designed to be centered once with a precision test bar and then left that way.
Then used as a normal self centering chuck . Put the material in and turn it to an accurate center.
I guess that for very small movements it would work ok.
 
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RoyB,
You don't need much to hold a barrel for chambering. I have a cathead on either side of my headstock. The 4 screws on either side have 1/4" copper pressed into them. No slippage.
If I machine something larger and take big cuts, the Bison 6 jaw comes out.
Butch
 
J. Valentine said:
You should not offset the chuck on the backing plate to center a job.
You are getting away with it at low speed but if you jack up the spindle speed the lathe is going to shudder if the chuck is off center.
If you do this over a period of time it might damage the spindle bearings not to mention affect on finnish.
Click to expand...

That's the way adjust tru chucks work. They use 4 set screws working against a collar on the backing plate to move the chuck on the backing plate to center the work piece. And yes, if you have to move the chuck much off center, the lathe will be out of balance at higher speed just as it would be if you have a work piece set up off center in a 4 jaw chuck. You can set up an adjust tru chuck to center on the outside for repeating work on identical pieces or you can use it to dial in an interior hole such as indicating in rifle barrels.
 
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guys,
i have a question on the jaw truing process described here.
the process is to load the jaws outward against a ring, and then true the inner surface of the jaws, then reverse and load the inside and true the od of the jaws. the problem i see with this is using the back side(wrong) of a thread for the corrected surface. loading the od when truing the id...but in use you expect to load the id when using the id.....differences in thread /thread wear means the truing may not be so true.

i did what one person recomennded...load the back of my id jaws, bore, then relieve the id that was under load. when i do the od of my jaws, i would do something similar.

mike in co
 
Since I started this thrread, I should probably let everyone know how I have resolved my issue.

I did get a new 4 jaw chuck off Ebay for $75. It is just a cheap one almost identical to my old one, made in China I'm sure. But it is straight, at least for my purposes.

One comment I wanted to make about holding the barrel and adjusting it in the chuck; I use a business card folded over in half lengthwise and wraped around the barrel between the jaws and the barrel. This gives me a no-mar way of holding the barrel and also keeps the pressure points kind of short and flexible. The other end is held by the spider screws at the left end of the spindle, again with a business card wrapped around to eliminate marking up the barrel.

Thanks again for the helpful comments.

Larry
 
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