This is a working demonstration of a mechanical iris diaphragm.
WARNING :- Please note the tolerances are a bit tight and depending on print orientation it may require a bit of cleaning.
Will post photos and videos later.
Early Video :- http://www.youtube.com/watch?v=fLSfJjS7QUE
Better but short video :-
18 w x
18 d x
7.087 w x
7.087 d x