Correct Answer - Option 1 : base circle
Terms Used in Gears:
Module (m): It is defined as the ratio of the pitch circle diameter to the number of teeth of a gear.
Pitch circle: It is the imaginary circle on which two mating gears seems to be rolling.
Circular pitch: It is the distance from the point of one tooth to the corresponding point of the adjacent tooth measured on the pitch circle.
Pitch circle diameter: It is the diameter of the pitch circle.
Addendum Circle: It is the circle drawn through the top of the teeth and is concentric with the pitch circle. It is also called the Outside circle.
Dedendum circle: It is the circle drawn through the bottom of the teeth. It is also called the root circle.
Base Circle: It is the circle from which the involute tooth profile is developed.
Addendum: It is the radial distance of a tooth from the pitch circle to the top of the tooth (or addendum circle).
Dedendum. It is the radial distance of a tooth from the pitch circle to the bottom of the tooth (or dedendum circle).
Land: The top land and bottom-land are surfaces at the top of the tooth and the bottom of the tooth space respectively.
Working depth: This is the distance of engagement of two mating teeth and is equal to the sum of the addendum of the mating teeth of the two gears. It is the radial distance from the addendum circle to the clearance circle.
Whole depth/Total depth: This is the height of a tooth. It is the radial distance between the addendum and the dedendum circles of a gear. It is equal to the sum of the addendum and dedendum.
