A low carbon steel bar of 147mm diameter with length of 630mm is being turned with uncoated carbide insert. The observed tool lives are 24 and 12 for cutting velocities of 90m/min and 120mmin respectively. The feed and depth of cut are 0.2mm/rev and 2mm respectively. Use the unmachined diameter to calculate the cutting velocity.
When tool life is 20min. the cutting velocity in m/min is
(a) 87 (b) 97 (c) 107 (d) 114
Neglect over travel or approach of the tool. When tool life is 20min, the machining time in min for single pass is
(a) 5 (b) 10 (c) 15 (d) 20