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Chuck question!

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Flat fender

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#1
Hello, I have a 8" three jaw Chuck, I Belive is a "Union" brand on my Sheldon Lathe (D-1-3 mount). It has nearly .012 of runout on most anything clamped in it, the jaws seem very sloppy in it. I've taken it apart and cleaned it. The body of the chuck runs true. Is there any fix to this ?, or is it new chuck time ?. I have a 4 jaw that runs fine and the spindle bearings seem ok on the lathe itself. Limited experience on my end, LOL.

Thanks, Flatfender
 

tweinke

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#2
I'm thinking if the jaws are loose probably time for a new chuck. Lets see if anyone with more knowledge chimes in though.
 

kd4gij

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#3
Do a search for grinding the jaws. You probably do need a new chuck, but grinding the jaws will get you by for awhile.
 

Ulma Doctor

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#4
.012" runout is not really a big deal.
if you are reducing the diameter of roundstock, the newly turned portion will be concentric with the axis of the lathe anyway
you can grind the jaws with a dremel in a holder on the lathe compound
but it would be best to do that with jaws that are loaded.
i did and old chuck that had .020" and reduced the measurable runout to right about .004"
i made a short video
 

Flat fender

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#6
Thank's for the info, I'll most likely try the diegrinder fix, when time permits. I will keep looking for a decent used replacement as well.

FF;)
 

Bob Korves

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#7
here is a video that shows a cheap way to load the jaws.
I would try another method. First, I think there is a possibility of the pieces flying out of the jaws, second, even with pieces carefully cut to the same lengths there may be differential loadings induced due to placement, widths of jaw slots and jaws, etc. which might cause concentricity errors.
 

chips&more

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#8
Depending on what your lathe needs are? Will govern your decision. If you will only use the lathe for non-critical parts. Then leave it alone. If you want to make meaningful parts. Then I would get a new chuck…Dave
 

Silverbullet

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#9
There are some good videos on YouTube to help show the process. Sometimes seeing is better then reading. Also there are many kinds and brands of chucks. My logan came with a three chuck it was trashed then but I reground the jaws and it's been useable for thirty years. I also own a six jaw chuck and I'd never have a lathe without one after using it. Between the 5C collets and the four jaw I'm set . Do your research see what you want and like then do your shopping , deals can be found on craigslist and other places.
 

MrWhoopee

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#10
Before you get too carried away, try snugging your piece of stock (not tight, just snug), then indicate, tap the jaw on the high side with a soft hammer, snug a little more, indicate and tap again, lather, rinse repeat. You may find that you can actually get the part to run true (or at least much closer).
 

Jimsehr

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#11
Check to see if you can turn down the step on the back and make it a set true by adding 4 screws. Then set it like a 4 law.
 

KBeitz

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#12
I have fixed chucks with a diamond dremel chain saw stone chucked up in the tail stock.
I very lightly tighten up the chuck jaws on the bit and push the tail stock into the chuck.Stop tighten
the chuck jaws and push again...
 
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