Following are the common terminologies used in Gear Hobbing Machines.

• Pitch Circle: The circle, the radius of which is equal to the distance from the centre of the gear to the pitch point.
• Pitch Point: The point of tangency of the pitch circles of two meshing gears, where the Line of Centers crosses the pitch circles.
• Addendum:The radial distance between the Pitch Circle and the top of the teeth
• Dedendum: The radial distance between the bottom of the tooth to pitch circle
• Module: Ratio of Pitch Diameter to the number of teeth
• Pressure Angle:Angle between the Line of Action and a line perpendicular to the Line of Centers.
• Root Circle: The circle that passes through the bottom of the tooth spaces.
• Face: The working surface of a gear tooth, located between the pitch diameter and the top of the tooth.
• Face Width: The width of the tooth measured parallel to the gear axis
• Working Depth: The depth to which a tooth extends into the space between teeth on the mating gear.