# Need help with South Bend 3-jaw scroll chuck.



## Old Rivers (May 20, 2018)

I have a 5" three-jaw South Bend scroll chuck I am trying to dismantle for cleaning The chuck is very dirty, but has some external but no internal rust. 
I got the back off the chuck, which uncovered the three screws which I removed.

Here is my problem: I need to remove the scroll pinion next, and there is a very small slotted setscrew located near the chuck body OD (see photos). I can only turn this screw a few degrees before it becomes impossible to turn. 
I rotated the pinion as I attempted to remove this screw, and discovered that when I apply CCW torque to the tiny screw the pinion rotation becomes more difficult. The pinion will move very slightly when I try to loosen the tiny screw. When I turn the little screw CW, the pinion will turn freely as the interference disappears. 
Does anyone have an exploded view of this chuck, or any suggestions? How do I remove this tiny screw?
Thanks for any suggestions.

Bill


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## GrayTech (May 20, 2018)

Sounds like the pinion may have to be turned to a specific orientation to remove the screw. Screw may have some kind of cam to it. 
PS, never done this, just going by what you described.


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## Old Rivers (May 20, 2018)

GrayTech said:


> Sounds like the pinion may have to be turned to a specific orientation to remove the screw. Screw may have some kind of cam to it.
> PS, never done this, just going by what you described.



GrayTech,

As I mentioned in my post I did try what you suggest, I rotated the scroll pinion through at least one revolution while trying to loosen the setscrew. 
Setscrew remains stuck.

Bill


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## Chuck K (May 20, 2018)

The set screw probably has a bur on it that hits when you start to loosen it.


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## mikey (May 20, 2018)

Bill, that little screw is a shoulder screw. The shoulder runs in a circumferential slot in the pinion body; this keeps the teeth on the end of the pinion engaged in the scroll. There is nothing that should interfere with this so if the screw is stuck then I'm going to guess that the shoulder screw is bent. When you turn it, it is taking up whatever space there is in the slot and it binds. 

Unfortunately, I know of no way to remove the screw other than to try and force it out. If this were me, I would make a hardened bit that precisely fits the slot - square like the slot, not tapered like a screwdriver bit. I would put that hardened tool in the chuck on the mill or drill press, clamp the stuck screw under it and use controlled torque to turn it out. You won't have many chances at this so I wouldn't just use a regular screw driver on it.


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## Old Rivers (May 20, 2018)

mikey said:


> Bill, that little screw is a shoulder screw. The shoulder runs in a circumferential slot in the pinion body; this keeps the teeth on the end of the pinion engaged in the scroll. There is nothing that should interfere with this so if the screw is stuck then I'm going to guess that the shoulder screw is bent. When you turn it, it is taking up whatever space there is in the slot and it binds.
> 
> Unfortunately, I know of no way to remove the screw other than to try and force it out. If this were me, I would make a hardened bit that precisely fits the slot - square like the slot, not tapered like a screwdriver bit. I would put that hardened tool in the chuck on the mill or drill press, clamp the stuck screw under it and use controlled torque to turn it out. You won't have many chances at this so I wouldn't just use a regular screw driver on it.



Mikey,
Makes perfect sense.
I'll attempt the solution you suggest.
Thanks,
Bill


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## Nogoingback (May 21, 2018)

Soaking it in some Kroil or other lubricant first wouln't be a bad idea either.


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## markba633csi (May 22, 2018)

With those 3 screws out you should be able to remove the back cover and see the scroll- maybe you can clean and reassemble without
needing to take the pinion retainer and pinion out?  Assuming you can't get that stubborn screw out..
Mark


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## Old Rivers (May 22, 2018)

markba633csi said:


> With those 3 screws out you should be able to remove the back cover and see the scroll- maybe you can clean and reassemble without
> needing to take the pinion retainer and pinion out?  Assuming you can't get that stubborn screw out..
> Mark



Mark,

Yes that tiny screw is stubborn... my home made extraction bit failed to remove it.

For the life of me I can't figure out how to expose the scroll. I have removed the chuck back cover (with the spindle threads), and then removed the rest of the screws which are covered by the back plate. How do I remove the scroll back plate which is slightly recessed inside the chuck body?
The pinion fits in between the scroll and this recessed back plate, so I don't see how the pinion is interfering with removal of the plate. There is no rust, and I've oiled everything. My photos in the first post show this inner plate.
I'd love to see an exploded view drawing of this chuck.

Bill


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## 38super (May 22, 2018)

If this is a Cushman style chuck, the split is mid body and not at the back plate.


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## Old Rivers (May 22, 2018)

38super said:


> If this is a Cushman style chuck, the split is mid body and not at the back plate.



.38Super,

The chuck is a 5", stamped with South Bend logo. The body is one piece, the only seam/split is near the back of the chuck where the spindle thread back plate attaches. There is only one pinion, located approximately mid-body.
The pinion is located in between the scroll and the internal, slightly recessed back plate.  

Bill


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## dlane (May 22, 2018)

It should come apart as is


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## Old Rivers (May 22, 2018)

dlane said:


> It should come apart as is



dlane,

Can you think of anything that would prevent the recessed, internal back plate from falling out once the screws are removed?

I slapped the chuck pretty firmly on a block of wood and it doesn't budge.

Bill


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## dlane (May 22, 2018)

My SB 8” chuck split at the pinions, but it was a tight fit , did you soak the fit with Penetrating fluid


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## derf (May 22, 2018)

The pinion has a pilot nose that is supported by the cover plate. The pinion must come out before the plate will move. Dive in and drill the screw out....replace it later.


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## Old Rivers (May 22, 2018)

derf said:


> The pinion has a pilot nose that is supported by the cover plate. The pinion must come out before the plate will move. Dive in and drill the screw out....replace it later.



derf,

Good to know, thanks. 
I did drill out the screw. Using a close fitting pin as a depth gage in the set screw's hole, it seems like the annular groove in the pinion is clear in the set screw area... but try as I might I can't extract the pinion. Pinion rotates freely and turns the scroll. I can't figure out a way to grip the pinion and tug on it via the 5/16" square chuck wrench recess.

Bill


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## benmychree (May 22, 2018)

The back plate of the chuck can be removed by removing the chuck jaws and driving against the scroll with a soft drift, but the pinions MUST be removed first because they bear against the back of the scroll ring.


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## Old Rivers (May 23, 2018)

After cleaning up the square key hole in the pinion I discovered a small axial hole through the pinion. I managed to grab onto this with a small sheet metal screw which allowed me to extract the pinion and dismantle the chuck. A small burr near the pinion retaining setscrew was making pinion removal difficult.

Bill


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## Old Rivers (May 23, 2018)

Different topic, what should I use for lubricant when reassembling this chuck?

Bill


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## mikey (May 23, 2018)

Bill, I use Super-Lube Grease on the rear of the scroll where the pinions contact and on the pinions and shoulder pins. I put a light coat of grease inside the chuck body where the scroll runs to reduce friction and discourage rust.

I use light coat of Super-Lube Oil on the front of the scroll, the jaws and jaw guides.

I also use a light coat of Camellia oil on the chuck surface to discourage rust in the Hawaiian climate.


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