Marco and Nicholas
You guys must have a different press design from mine. First, the nuts on my press are very thin (1/8") to clear the press when opening or closing the press. They look like specialty nuts. The nuts you guys posted would not fit this press. Second, they are definitely not locking nuts. I've never seen locking nuts this thin. If you like, I can post a picture.
I considered using lock-tight, but I am afraid to ruin the threads or the nuts.