In a turning operation, a single pass must be completed on the cylindrical work piece in 6 mins. The work piece is 550mm long and 140 mm in diameter. Using a feed = 0.2 mm/rev and a depth of cut = 40 mm. What cutting speed must be used to meet this machining time requirement?  

(c)   Consider a horizontal true centrifugal casting operation.
(i)   A metal tube (length = 3 m) is to be made with the outer diameter (OD) = 0.3 m and inner diameter (ID) = 0.25 m. What rotational speed (in rpm) is needed if the G-factor is required to be 70?
(ii)   Why does impurity tend to stay at the inner surface in this operation?
(iii)   Semi-centrifugal casting is another metal casting method. Suggest one product that would be made by semi-centrifugal casting.