2.Gear Tooth Terminology
The following definitions apply to the three drawings shown below.
- Heel and Toe identify the ends of the gear tooth. Imagine you and 12 other people are standing
in a circle facing each other, your toes are pointing inside of the circle and your heels are pointing
outside of the circle.
- The Toe end of a ring gear is on the inside diameter of the gear.
- The Heel end of a ring gear is on the outside diameter of the gear.
- The Pitch Line is an imaginary line that divides the upper and lower halves of the gear tooth
- The Pitch Point is the theoretical point where the pitch lines of both meshing gear teeth meet
while rotating relative to one another.
- The Root Line is an imaginary line that indicates the bottom of the meshing gear tooth contact area.
- Face and Flank identify the area in the contact area of the gear tooth.
- The Face of a gear tooth is the upper half of the gear tooth contact area.
- The Flank of a gear tooth is the lower half of the gear tooth contact area.
- The Drive Side and Coast Side of the gear tooth identify the sides of the gear tooth used under
acceleration and deceleration.
- The Drive Side is the convex side of the gear tooth and is used during acceleration and steady
- The Coast Side is the concave side of the gear tooth and is used during deceleration.
- Backlash is the endplay between the gear teeth as the gear sets rotate relative to one another.
- Clearance is the distance between the top of one gear tooth and the bottom of the area between two
gear teeth it is meshing with.
- Undercut is the bottom of the area between two gear teeth where no gear-to gear contact should be made.