Thanks to reading on here about how to break lose a really badly rusted shut vice, I finally got it open. It took a week of electrolysis, then some PB and sitting for a few days, then a 1 hour heating on the forge, to red-orange. It finally then broke loose! After it cooled, I turned the vise on its side, screwbox up, and squirted PB into the end of the box so it soaked through the threads. I then managed to work the screw back and forth, going a little farther each time.
I think the previous owner re-assembled it wrong, which made breaking it loose very hard. The washer between the screwbox and stationary part of the vise completely covered the "key" on the screwbox which inserts into the vise (I thought it had broken off!). This meant that the whole screwbox and vise handle assembly rotated free. I had to drill a hole through the spindle at the back of the screwbox and insert a punch to keep it from rotating while I gently tapped the handle to rotate the screw. This finally worked.
So if you are working on your rusted, listen to the folks here. Patience, PB Blaster, and a good heat on the forge will eventually break 'er loose.
How did you fix your vise?
