Material of Shaft:
Cast Iron is very rare for shafting nowadays, though a century ago, things were different. The primary problem with Cast Iron is brittleness. This makes it unsuitable as there are few applications where failure would not have serious secondary consequences.
Further, wrought material is readily available and shafts are easily machined from it without much loss of material. This cancels out the advantage of Cast Iron that it is already close to final form when cast and needs less machining. For large shafts with significant turning material loss, forgings are economical and very strong.
A fairly modern development of Cast Iron is Malleable Iron (SG Iron, Spheroidal Graphitic Iron). However, even this versatile material is not much used for shafts The most commonly used shafting materials are EN-8, EN-9 or EN-24 in rolled condition. For higher strength forged material can be used. The residual stresses during the process of rolling or forging are removed by normalizing heat treatment.