I usually post this for he swivel nut and handle replacement; tweaked for a main screw handle::
Get a 8-10” bolt in 1/2” (Or whatever your hole is...); also get a matching Jam nut. Grind the points off the hex of the bolt (cosmetic cleanup), and string it through the hole drilled in the main screw.
Run the jam nut down and jam it into the bottom of the threads of the bolt. Cut off most of the excess bolt. Peen the remainder of the bolt threads into the nut as flush as you can, and file flat.
The last step is again cosmetic: Grind the points off the now captive Jam nut. You have just made a new handle for the vise…