Answer
Therefore facewidth should be kept = 28mm from table 13-2
Work Step by Step
$Pitch Diameter, d=N ∗ m=20∗2=40 mm$
where, N = number of teeth
m= module
$Lewis form factor, Y = 0.322$ ; for 20 teeth with 20degree pressure
angle
$Pitch line velocity, V=(pi ∗ d ∗ n)/60$ ; where n = speed in rpm
therefore $V=(3.14∗40∗0.001∗200)/60=0.419 m/s$
$Velocity Factor, K=(6.1+V)/6.1$ ; for cut or milled profile
therefore $K=(6.1+0.419)/6.1=1.069$
$Tangential load, W=(60000∗h)/(pi ∗ d ∗ n)$ ; where h is power in kW
therefore $W=(60000∗0.5)/(3.14∗40∗200)=1.194 kN =1194 N$
$Facewidth,F=(K∗W)/(sigma ∗ m ∗ Y)$ ; where sigma is bending stress
$Facewidth,F=(1.069∗1194)/(75∗2∗0.322)$
$Facewidth,F=26.4 mm$
Therefore facewidth should be kept = 28mm from table 13-2
