Making progress with rollerball

[NGLJ]

Making progress with rollerball kitless using an M13/10 x 1 combination - see attached. It is an Alumilite cap and barrel, and Acrylic section (all from William Wood-Write). I like slim pens, and have made some M10/7 x 1 with Cross style refill. I might try an M12/9 combination for rollerball. If I do what is usual for thread spacing?

 

[rixstix]

For me, m9.5 x 0.8 works better (actually 3/8" UNEF tap die) than m9 x .75