Hi, I know basics of gear design but have never designed a gear before. I want to know, while designing a spur gear what is defined first 1] Pitch Circle or 2] Base Circle ? In case. if base circle is defined first, then how to determine its diameter ? Lot of design materials explain how to design a gear on a very surface level. I have gone through lot of material on gear design before posting this querry but I was unable to find the answer. plz guide me.