Stepped Shaft (Shaft in Series):

A shaft can consist of a number of small shafts of different cross-sections in series. it is known as stepped shaft .

In the analysis, primary torque resisted by each portion is found. Because of torque, the angle of twist in each of the portion is found and the shear stress in each of portion is found. Then we may draw the torque diagram, shear stress diagram and the angle of twist diagram.

When analyzing, the most significant points are :

 (a) The toques produced at the ends of any portion are equal and opposite.

 (b) At common points, the angle of twist is the similar.