Required “Hub Diameter”
d 3, should be calculated using the formula below for each specific application:

T = Base torque to be transmitted (ft-lbs)
Mt calc = Calculated torque & service factor (ft-lbs)
Mt cat = Catalog rating of ETB or STC assembly
Pax = Axial load/thrust to be transmitted (lbs)
d = Shaft diameter (inches)
Ps = Pressure applied to shaft (psi)
Ph = Pressure applied to hub (psi)

D2 = Hub bore (inches) taken from specification tables
Ph = Contact pressure applied to hub bore (psi) taken from specification tables
YP = Yield point of hub material
C = Stress reduction factors which take into account the ratio of hub length “B” to the expanding bushing length L1 used in the specific application
a: 1.0 for B = L1
b: 0.8 for B = 1.5 x L1
c: 0.6 for B ≥ 2.0 x L1

Note: C is a linear function between values of 1.0 (B = L1) and 0.60 (B = 2.0 x L1) and is constant at a value of 0.6 for B> 2.0 x L1.