The older Nova was closed and opened with a rod in one hole and a bent
handle in the other. It has the same jaws as other newer models. I had
trouble getting the jaws tight enough with the two rod chuck. The Super
Nova uses a hex wrench with a "T" handle to adjust the jaws. I t will
tighten too much if I am not careful. The Super 2 has a closed back and
the "T" handle. Both are bigger phyusically than the old Nova chuck.
You will need to get an insert to fit your lathe spindle. Usually they
come with the chuck. Some sellers charge you extra for the insert. You
must use and insert or a threaded chuck to fit your lathe.

The worm screw is used when you want to screw the chuck into the blank.
You fasten it into the jaws and literaly screw it into the blank after
first drilling a hole in the blank since the screw is about 1/4" in
diameter. I have used the screw but don't like it. It is much easier to
turn a tennon and use that in the jaws of the chuck than screw a "bolt"
(the screw) into the wood piece.

The jaws of the Nova are interchnagable for all Nova chucks. The
standard is about a 50mm I think. You can get other dimension jaws that
will squeeze a smaller tennon. All the jaws can be used in an expansion
mode to fit a dovetail recess and expand the joaws into it to hold the
blank.

Nova (Technatool) has a web page that shows their jaws and the various
attachements.