timing pulleys

I was just looking at making timing pulleys. Obviously these are made with an A-Axis added to a mill. I think I can make some simple ones with an ordinary XYZ gantry.

I was just looking at some of the specifications of belts: http://bbs.homeshopmachinist.net/showthread.php?t=38465

I guess it’s a matter of making two circles and then some lines to make the teeth?