I have a strange vise. Its been hanging around for a while and I never delt with it, except to move it twice while waiting to setup a real shop.
Having offered it up to someone I started taking a closer look and noticed an oddity. It won't close past 2" open.
Seems like it wants too then it pops back.
I took it apart and looked the threaded rod has a spring over it which won't allow it (I think the nut may be worn down a bit too, haven't had a chance to check that).
Pics n info here: