I always use a 5/16x14 pin works very well until you can a broken butt to take a pin out of.
Hope this helps I've used one for ten years just fine,
Jerry 2
I believe the actual threading is 3/8x14...slightly modified. The threads are rounded a bit.
I charge $12 plus shipping for the Cue Tec style lathe pin.
http://www.cuesmith.com/index.php?menu2=menu_accessories&page=lathe_supplies