The pin centres are 10.16667mm and the in feed is 2.475946 acording to the computer program I downloaded from Marve Klots web site , gashed with a woodruff cutter just past centre to give the teeth some rake , hardened and tempred to straw , the worm eyeballed to 4 degrees so set the wheel to that , tooth depth is 1.51 fed it in and started cutting , the worm fitted well straight with no back lash and just one heigh spot that will polish out .