Input data:

Pitch Diameter, in:	D
Bore Diameter of Shaft, in:	Dh
Root Diameter, in:	Dre
Radial Height of Tooth In Contact, in:	h
Effective Face Width, in:	Fe
Application Factor (Table II):	Ka
Load Distribution Factor (Table IV):	Km
Life Factor Limited by Fatigue (Table III):	Lf
Life Factor Limited by Wear, Flexible Splines (Table VI):	Lw
Number of Spline Teeth:	N
Chordal Tooth Thickness at Pitch Line, in (MIN):	tc

Torque, in-lb = 63,000 * HP / n:

T

Allowable Shear Stress (Table I):	Ss
Allowable Compressive Stress (Table V):	Sc
Allowable Tensile Stress (Table VII):	St

Output data:

Allowable shear stress in shaft,S_s2(PSI) :	S_s2=Ss*Lf/Ka
Shaft Stresses S_s1(PSI):	S_s1=16*T*Dre/(Pi*(Dre^4-Dh^4))
Margin of safety (needs to be > 0):	S_s2/S_s1-1

For internal splines cick here: