Conventionally for cast iron as well as sg iron carbide tools in coated as well as uncoated grade are used. Low cutting speeds as well as less tool life are the 2 constrants which makes cast iron machining more tedious and high machining cost. Sumitomo has made pioneering efforts in usage of CBN as a cutting tool material in general and cast iron machining in specific. Their long experience of tool failure analysis and efforts to improvement tool life with changing grade compositions, binders, alloys, coating and edge treatment has resulted in 4 different grades for cast iron as well as ductile cast iron machining. Motherson CBN being most hard material ideally recommended first choice for higher speed, same resulted in productivity, efficency and lower machine cost for area of cast iron. Motherson CBN encures excellent surface finish, reduction in cycle time, reduction in tool change time, consistency of bore while machnining long lengths in close tolerances. Sumitomo offering BNX10, BN500, BN600 and a Grade BNS800 which covers the whole range of cast iron compositions.