The transverse pitch of a helical gear corresponds to the pitch of a spur gear with the same number of teeth and the same pitch diameter. It is measured in the plane rotation of the gear. (See Figure below)
Transverse diametral pitch (D.P) = 3.1416 (Transverse circular pitch (C.P.)
NORMAL PITCH
The normal pitch of a helical gear is the pitch of the tool used to cut the teeth. It is measured in a plane perpendicular to the direction of the teeth.
Normal diametral pitch (D.P.) = 3.146 ( Normal circular pitch (C.P.)
NORMAL PRESSURE ANGLE
Normal pressure angle is the pressure angle in the normal plane of a helical gear tooth.
