Diametral Pitch
Key:
Do = Outside Diameter.
a = Centre distance.
P = Diametral pitch.
N = Number of teeth.
N1 = Number of teeth gear 1.
N2 = Number of teeth gear 2.
Outside diameter
Do = (N + 2) / P
Centre distance
a = (N1 + N2) / (2 * P)
Module
Key:
Do = Outside Diameter.
a = Centre distance.
m = Module.
z = Number of teeth.
z1 = Number of teeth gear 1.
z2 = Number of teeth gear 2.
Outside diameter
Do = m * (z + 2)
Centre distance
a = m * (z1 + z2) / 2