How does one use a cathead with a steady-rest to center a shaft with a
rough surface (a rough casting or hot rolled steel)? When one dials in
the cathead by adjusting the bolts on the cathead is the cathead being
supported by the bottom 2 supports of the steady rest or is the steady
rest closed and all 3 supports of the steady rest touching the
cathead? Or is the cathead hanging out in space unsupported?

I am not sure what you mean by "centering a part " with a cat head and
steady rest.
The steady would be out of the way while the cathead is being clamped to the
shaft and adjusted for zero runout.
Then the steady would be moved over the cathead. How would you know how
where to to place the bottom rollers
if you do it the otherway? At least this is my experience, FWIW. Jim.

JOSEKIND wrote in message
om...
How does one use a cathead with a steady-rest to center a shaft with a
rough surface (a rough casting or hot rolled steel)? When one dials in
the cathead by adjusting the bolts on the cathead is the cathead being
supported by the bottom 2 supports of the steady rest or is the steady
rest closed and all 3 supports of the steady rest touching the
cathead? Or is the cathead hanging out in space unsupported?

(JOSEKIND)

How does one use a cathead with a steady-rest to center a shaft with a
rough surface (a rough casting or hot rolled steel)? When one dials in
the cathead by adjusting the bolts on the cathead is the cathead being
supported by the bottom 2 supports of the steady rest or is the steady
rest closed and all 3 supports of the steady rest touching the
cathead? Or is the cathead hanging out in space unsupported?

I haven't worked that way. Maybe you can dial in a test piece in the cathead
in the steady rest, take it out and put in the rough piece and go from there?

Would it be simpler to put the work (rough piece) between centers, turn a neck
for the steady to ride in, and go from there? [I re-read this. I have such a
limited vocabulary these days. lol]

You can also make a cat's head to use at the dead center end of the work, a cap
with four adjustinting screws, and a 60 deg indent at the center of its face
to fit in the dead center.
Frank Morrison