@John OKeefe - I believe that the US equivalent of an M3 is a #4. It could be worth trying a 4 x 1/2 if you have one at hand before spending too much time hunting down an elusive M3.
Jankeesvw
over 8 years
I printed this yesterday in red PLA: https://youtu.be/n8Pgod_S4vg (print took about 8 hours)