Is there a formula to determine the correct number of teeth for a circular gear of radius x in order to properly mesh with a toothed shaft with gear teeth of spacing
![Boston Gear YA12 Spur Gear, Steel, Inch, 20 Pitch, 0.313" Bore, 0.700" OD, 0.500" Face Width, 12 Teeth: Amazon.com: Industrial & Scientific Boston Gear YA12 Spur Gear, Steel, Inch, 20 Pitch, 0.313" Bore, 0.700" OD, 0.500" Face Width, 12 Teeth: Amazon.com: Industrial & Scientific](https://m.media-amazon.com/images/I/71UWGGPRZRL._AC_UF894,1000_QL80_.jpg)
Boston Gear YA12 Spur Gear, Steel, Inch, 20 Pitch, 0.313" Bore, 0.700" OD, 0.500" Face Width, 12 Teeth: Amazon.com: Industrial & Scientific
![design - Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly? - Engineering Stack Exchange design - Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly? - Engineering Stack Exchange](https://www.unf.edu/~aschonni/Research/design%20analys%20fabr%20verific/gear%20tooth/Gear_design_analysis_files/image005.jpg)