According to above description we know, the pressure
angle 2 α becomes smaller in the tip-end, so the top-land
width becomes breadth than that in the big-end. Due to the
tooth space is narrow, the top-land surfaces will be cut in the
process of generation of face gear, which phenomena is
called as undercutting of tooth of face gear. Avoidance of
undercutting of face gear teeth can be achieved by limiting
the inner radius of the face gear 1 R [8,9].