The last one that I did, as recently as last week, was 9mm even.
Your declaration of 9.9mm seems a little odd to me.
9mm is .354", 9.9mm is .389". Care to measure it again?
Only because I'm a true believer in the axiom, "measure twice, cut once".
Is the pin a constant thread or is it sectioned, blank, thread, blank?
A pic would be helpful also.
I think I can help you but you're going to have to provide a little more info.
KJ