spur gear rack tooth distance question.

I am planning on using 14.5deg 20 pitch rack for my cnc router. I
know that the pitch stands for the distance between teeth but
measurement or ratio is it (inches, mm etc.)

I was hoping to drill holes in my structure before I have the actual
rack. I was planning on drilling and tapping my rack in between its
teeth. If I knew the distance (in inches or mm) between the teeth I
could go ahead with building the structure. (If that makes any
sense)

Thanks in advance

Troy