Say you need to turn the end of a bar that is too big to go through the lathe headstock and too long to fit between centers (or the center-rest if you have one)...
Here are some answers:
Arcane suggests: If you have a milling vise setup that attaches
to the cross slide for your lathe and a boring head with a MT3 taper,
clamp the shaft in the vise, center it on the spindle and then use the
boring head to reduce the end.
Dan suggests: There was someone who did an interesting trick. They welded a smaller
piece to the end and chucked it up. Supported the far end in a steady
rest. Then they turned down the original bar and parted it. Rotate
Better yet, just start with stock longer than required an part off the chucked bit.
My idea, specific to my 3in1 machine:
Using something of suitable height, like the angle table (level, just for the height), make a vertical clamp that hangs outboard the lathe. Swing the head over to match and lock down, then use the X/Y to center. Once centered, use the boring head as above, with the cutter pointing inward. This would give me about 4' of length, and it would be easier to set up than removing the tailstock to use the lathe spindle.