Need help with South Bend 3-jaw scroll chuck.

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
 
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
 
My SB 8” chuck split at the pinions, but it was a tight fit , did you soak the fit with Penetrating fluid
 
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.
 
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
 
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.
 
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
 
Different topic, what should I use for lubricant when reassembling this chuck?

Bill
 
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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