In the case of power transmission sometimes that was a fluctuating or repetitive load comes on drive shaft or driven shaft in working condition. At that time shaft as well as gear or pulley which are mounted on the gear shaft is also comes under the fatigue loading. To determine the shaft diameter under dynamic condition we should consider length of shaft, diameter of pulley and gear, tension on pulley , rpm of shaft, distance between gear and pulley, pulley and bearing on which shaft is mounted, permissible stress of shaft material, fatigue load The main purpose of writing of this paper is to determine shatdiameter with different material and under the different permissible stress.Keywords: Shaft, fatigue loading Shear Stress, tangential force
