Number of Pairs of Teeth in Contact:

As illustrated in figure the arc of contact is P′ P″. All of the teeth lying in between this arc of contact shall be meshing along the teeth on other gear.

Gear Geometry

Number of teeth within the arc of contact (n) = Arc P′ P P′′ /Circular pitch (pc )

Or,

                                . . . (9.5)

The value of n should be > 1 and practically it lies among 1 and 2. The value of n shall be equivalent to contact ratio that is ratio of the angle of action to the pitch angle.