The tool life equation for HSS tool is VT0.14f0.7d0.4=Constant.
The tool life (T) of 30 min is obtained using the following cutting conditions: V = 45 m/min, feed = 0.35mm, d= 2.0 mm. If feed (f) and depth of cut (d) are decreased individually by 25% and speed (V) is increased by 25%, the tool life (in min) will be: