Gear Nomenclature

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.