I think calvary is right, but if this is a production "chucker" it may
have a lever (rather than a drawrod) that allowed the operator to
quickly release a kind of spindle cam lock that effectively swedged
the collet into the tapered bore, as I recall. If that spindle nose
had two threaded holes 180 degrees apart, that's possibly what it is.
in the meantime, I'd probably just tap the collet edges
counterclockwise and use some light judicious heat in the process, but
I'd try Calvary's idea first, see if there is a theaded hole in the
back of the collet that would allow you to thread in a bar and tap it
I *think* that it is a collet chuck which is opened and closed
by air pressure. The fitting on the side of the body suggests that,
though it does look more like a grease fitting than an air one.
The real test is whether, when the chuck is on the spindle,
whether the spindle and collet can rotate while the chuck body remains
stationary. I think that the apparently threaded hole in the side is
for a bar which keeps the chuck outer body from rotating while the
This is the sort of thing used for serious production runs, and
would normally have been mounted on a lathe with a turret toolpost and a
tailstock with a turret for axial feed tools.
If so -- it may need air pressure to loosen the collet so you
can unscrew it. Release the air pressure and a strong spring closes the
Check out whether my idea is possible first (by testing for
rotation of the spindle and collet without rotating the outer body. If
so, the other methods proably won't work.
I agree with Don that this is a pneumatic (air)activated collet chuck.
The hole on the side looked threaded (hard to tell with the loss of
focus). On the two that I have seen they were hard plumbed to prevent spin.
Hardinge has a good example:
my australian hercus 9 inch is a clone of your southbend.
in my collet chuck the collet sits in a tapered sleeve just like
yours. the outer fitting is different though.
the collet in mine is externally threaded down near the back end. the
draw tube that pulls the collet back into position is internally
threaded to screw on to the outside of the collet.
there is a pin in the tapered sleeve, about an eighth diameter and a
sixteenth deep, which mates into a groove along the rear of the
collet. this is presumably to stop the collet rotating as you screw up
the draw tube.
to get yours apart without damage I would make an annular piece of
metal that the whole lot could sit nose down into. sit this somewhere
get a piece of brass bar the diameter of the rear hole. place this
down into the hole to sit on the rear face of the collet.
with everything rigid so that the movement of the collet is the only
freedom I would give the brass bar a sharp rap with a ball pein
it should pop apart since only the friction of the taper is holding
from investigation of my collets the suggetion that you tap it
anticlockwise cant work if our collets are the same.
OOPs! Looked at pic #1 and posted. DoH!
It may screw in from the front, and require a three bladed handle that
fits the slots on the collet in order to unscrew it, if it is a 5c type
or similar collet, or there may be a set of holes for a pin spanner in
the back of the chuck.
"from investigation of my collets the suggetion that you tap it
anticlockwise cant work if our collets are the same. "
Oh, I didn't mean to attempt to unscrew it, only break the collet
loose from the taper, assuming there's just a lot of old coolant or
cutting oil gumming it up. I said counterclockwise meaning against the
direction of spin. (That's looking from the headstock to tailstock
perspective) But in anycase, Hardinge has some pretty good photographs
at their website showing a cross section of their various chucking
systems that can give a pretty good idea of what the concept is. (And
the drawbar) I really don't think air clamping is involved. Some of
the Hardinge chuckers have an identical fitting and I think it's just
for a spanner that threads into the hole for dissasembly, or to change
I got it figured out. The holes in the back are threaded, so I took
two 1/4-20 bolts, threaded them in on opposing sides and put them in
my vise so they wouldnt move. I then unscrewed the outer part. So it
seems that It takes a spanner wrench but the threaded holes threw me
off. The collets are Brown & Sharpe # 21. Anyone have any info? A
google search looks like they may hold up to 1 inch.