# Design of Flange Coupling

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## Design of Flange Coupling

Consider a flange coupling as shown in Fig. 1 and Fig. 2.

Let d = Diameter of shaft or inner diameter of hub,

D = Outer diameter of hub,

d1 = Nominal or outside diameter of bolt,

D1 = Diameter of bolt circle,

n = Number of bolts,

tf = Thickness of flange,

τs, τb and τk = Allowable shear stress for shaft, bolt and key material respectively

τc = Allowable shear stress for the flange material i.e. cast iron,

σcb, and σck = Allowable crushing stress for bolt and key material respectively.

The flange coupling is designed as discussed below :

### 1. Design for hub

The hub is designed by considering it as a hollow shaft, transmitting the same torque (T) as that of a solid shaft.

T = π/16 × τc { (D^4 – d^4) / D }

The outer diameter of hub is usually taken as twice the diameter of shaft. Therefore from the above relation, the induced shearing stress in the hub may be checked.

The length of hub (L) is taken as 1.5 d.

Reference by A Textbook of a Machine Design by R. S. Khurmi and J. K. Gupta