# 6 inch Union Chuck advice



## Bailey (Sep 24, 2013)

This chuck is off of a 1940 9A SB, took me 3 days to get it off the spindle.
I decided to take it apart clean it, all the parts seem to be in good shape so I'll give
it good cleaning and put it back together(hopefully).
What should I do for lube? 
I thought that I would give the gear side a light coat of lithium grease and the scroll side a small dose of
spindle oil. 
The jaws look like they could be reversed since they are 2 parts but there is little purchase
left of the jaw teeth, any ideas for replacement jaws for this?

Thanks for your help
Bailey


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## Chuck K (Sep 24, 2013)

The right way to clean up the existing jaws would be with a tool post grinder. Do you have a lot of runout with them or is the wear on the serations the only issue?  The fact that you have two piece jaws is a good thing.  You can make a set of soft jaws and machine them in place so that your part runs dead true.  Usually the issue with the older scroll chucks like that isn't as much the jaws as the wear in the scroll itself.  I have used a toolpost grinder to try to true them up in the past and found that it worked fine at the diameter I ground it but when I moved to a different diameter the scroll had so much wear that the jaws were off again.  But if you put a set of soft jaws on it you can just bore it to size when needed and it will be true.  Good luck.

Chuck


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## Bailey (Sep 24, 2013)

ARKnack said:


> First I am a total armature but I lubed mine with way lube when I tore mine apart. As for the ware, right or wrong, I would  use a boring bar and recut the surface along with the grooves. Find replacement parts that really work would be a SOB.p



I am unsure if I will have any gripping/holding issues in the shape there in now, if there is too much slip the boring bar suggestion sounds good.
So you just used way lube for the gear and scroll side when you put yours back together?
No doubt new parts couldn't be found and used ones would probably be worse that what I have.

Thanks


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## Bailey (Sep 24, 2013)

Chuck K said:


> The right way to clean up the existing jaws would be with a tool post grinder. Do you have a lot of runout with them or is the wear on the serations the only issue?  The fact that you have two piece jaws is a good thing.  You can make a set of soft jaws and machine them in place so that your part runs dead true.  Usually the issue with the older scroll chucks like that isn't as much the jaws as the wear in the scroll itself.  I have used a toolpost grinder to try to true them up in the past and found that it worked fine at the diameter I ground it but when I moved to a different diameter the scroll had so much wear that the jaws were off again.  But if you put a set of soft jaws on it you can just bore it to size when needed and it will be true.  Good luck.
> 
> Chuck



Chuck,

I have never used the chuck I am still working on getting the lathe put back together and while I am waiting for paint to dry decided to
take the old Union apart. My concern was the wear on the serrations which seems uniform on all the jaws, don't have a tool post grinder
but the previous poster suggested using a boring bar to recut the grooves which sound logical to me.
I have no way to check runout til I get the lathe running, have seen some posts re soft jaws, is there a vendor who would have soft jaw replacements
for an older chuck like this? Can't confirm the wear on the scrolls either, but that is definitely some good metal in this chuck.
Will check runout when I get the lathe and chuck back together and go from there, at least it will be easier to take the chuck apart the next time.

Thanks


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## lrsglory (Sep 25, 2013)

By way of suggestion, not trying to blow a big horn or anything. If you do make a set of soft jaws, pick one square tightening screw, blue it so you can always use it and it alone, when you use the chuck. Sounds silly but I have seen it work as far as repeatability. Might help for what its worth.


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## 4GSR (Sep 25, 2013)

First thing I would do is determine how much "slop" the scroll has with the chuck housing.  The scroll is the piece that has gear teeth on one side and a spiral square thread on the other side.  The scroll should be a snug fit, no more than a couple of thousand clearance.  If it has over .010" clearance or lots of slop in the scroll, it is wore out.  The can be built up and turned down to add a little life to them.  But if the square thread has any wear or damage,, it will not hold any part true when chucked on, without indicating in the part.

I will say with the few pictures attached, it does not appear to be much wear in that old chuck.  Give her a try!)


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## Bailey (Sep 26, 2013)

4gsr said:


> First thing I would do is determine how much "slop" the scroll has with the chuck housing.  The scroll is the piece that has gear teeth on one side and a spiral square thread on the other side.  The scroll should be a snug fit, no more than a couple of thousand clearance.  If it has over .010" clearance or lots of slop in the scroll, it is wore out.  The can be built up and turned down to add a little life to them.  But if the square thread has any wear or damage,, it will not hold any part true when chucked on, without indicating in the part.
> 
> I will say with the few pictures attached, it does not appear to be much wear in that old chuck.  Give her a try!)



Here are a few pics of the scroll side, I'll file any burrs or high spots down before assembly.
As suggested I put the jaws in and there is very little play/movement toward center.
I have the gear end soaking in evaporust tonight, since it can't be lubed and is sealed it is the only area that had any rust.
Tomorrow nite will put it back together and check for RO on the spindle at various diameters of stock.
Any suggestions for lube on the gear side before I put it back together?



Thanks
Bailey


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## Todd (Sep 26, 2013)

a chuck is one place where i would use grease.  i first used way oil when i cleaned out my 3 jaw, and as you can imagine the first time running the lathe at a high speed i had that nice strip behind the lathe and up the ceiling of way oil being slung out of the chuck.  so the secodn time that i took it apart i used some heavy bearing grease i had laying around, no slinging and lubed it just fine.  since the scroll plate covers it i have not had a problem of getting chips in there either.  from what i read grease is actually pretty common to use in 3 jaws.  


Todd


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## Ray C (Sep 26, 2013)

If you're looking for parts and possibly some assistance, this place was very helpful to me and graciously spent time on the phone to help me out. I believe 1-2 list members have done well by this place as well:
http://www.worldwidechuck.com/

Ray


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## Bailey (Sep 28, 2013)

Got the chuck back together, used multipurpose grease in the gear section and light coat of way oil on scrolls.
It went together smoothly.
Will check runout and report results.

First time taking a 70+ year old 3 jaw chuck apart.
Thanks to all for sharing their time and knowledge.

Bailey


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