i) Base circle

ii) Pitch circle

iii) Prime circle

Subject: Kinematics of Machinery

Topic: CAM Mechanism

Difficulty: High

i) Base circle: It is smallest circle that can be drawn to the cam profile.

ii) Pitch circle: It is a circle drawn from the Centre of the cam through the pitch points.

iii) Prime circle: It is smallest circle that can be drawn from the Centre of the cam and tangent to the pitch curve, for a knife edge and a flat face follower, the prime circle and the base circle are identical. For a roller follower, the prime circle is larger than the base circle by the radius of the roller.