gear question

How do I find the Center distances if I want to mate a 20Tooth Gear, 16 DP, 14.5 Pressure Angle, with a Pitch Diameter of 1.25in and Outer of 1.375in with a 60 Tooth Gear 16 DP, 14.5 Pressure Angle, Pitch Diamter 3.75in and a outer diameter of 3.875in?

Thanks for anyone who can help me out.

the exact meshing distance between two spur gears is determined by adding their pitch diameters, then dividing by two. (basically, you are adding the pitch radii)

Make sure to add about 3/1000s of an inch between your centers as your gears may grind if the meshing is too exact.

In this picture, pitch diameter is referred to as pitch circle:
http://www.sdp-si.com/D190/HTML/T26_1.jpg

Thanks I wasn’t sure if it was that simple. I thought it was more complicated than that… oh well.