One of the biggest annoyances using the precision screwless vise was loosening the jaw and accidentally unscrewing it from the T bracket which holds the cross bar that hooks into the base. After having it happen it again in the middle of a project I took the screw which connects the jaw to the T and turned it smooth starting 5 threads from the end.
|Middle section of screw turned smooth.|
I then ground a flat on the T right where it threads onto the screw. I then assembled the vise, threaded the screw into the T, and peened the flat to capture the screw. Now, no more accidentally unscrewing it.