Machine Design and Engineering

Solid Bolted Shaft Coupling Design Equations and Calculator.

Power Capacity P = π²NnD_pD²_bτ_y / 4

Key FS = πDNbLτ_y / P

Shaft FS = π²ND³τ_y / 8P

If, the bolts and nuts have same materials and FS, then:

Bolt diameter min. D_b = ( D³ / ( 2nD_p ) )^1/2

Where:

Symbols used:
D = Shaft diameter (mm)
D_p= Pitch circle diameter of bolts (mm)
D_b = Bolt diameter (mm)
n = Number of bolts
b = Width of key (mm)
L = Length of key and hub (mm)
P = Power transmitted (watt or in SI base units kg-m²-s^-3)
FS = Factor of safety
N = Shaft speed (rpm)
τ_y = Shear yield stress (Pa)

Reference:

Mechanical Engineers Databook, Carvil