Thanks to some good suggestions from fellow LJ’s (derosa and Kova) I secured the nut by using a nylon lock nut that I managed to get in town today (the local co-op only has 10 & 12mm nylon lock nuts) and just to make doubly sure I used a pin as well. This is probably over engineering, but I don’t want the nut to come loose after the jaw has been glued together.
I have some 5mm nails which supplied me with a tight press fit pin
After peening the pin, I’m sure it will stay there forever and a day :-)
-- There are some things that money can't buy - Manners, morals and integrity