Tooth Profile of an Involute Gear

Abstract

In general, the tooth profile of a rack may be curved, and the profile angle $\phi^{\rm A_r}$ would then vary from one point of the tooth to another. We now consider a particular rack, in which the teeth are straight-sided. This is the basic rack which we use to define the tooth shape of an involute gear. The profile angle for this rack is constant, and the value of the constant will be represented by the symbol Φ_r, which is called the pressure angle of the basic rack. Thus, for the basic rack used to define involute tooth profiles,

$$\phi^{\rm A_r}=\rm constant=\phi_{\rm r}$$

((2.1))