A conventional lathe and a $$CNC$$ lathe are under consideration for machining a given part. The relevant data are shown below :

The machine preferred for producing $$100$$ pieces is

What is the approximate $$\% $$ change in the life, $$t,$$ of the tool with zero rake angle used in orthogonal cutting when its clearance angle, $$\alpha ,$$ is changed from $$10$$ to $$7$$ deg?

(Hint: flank wear rate is proportional to $$\cot \,\alpha $$)

In orthogonal machining operation, the chip thickness and the uncut chip thickness are equal to $$0.45mm$$. If the tool rake angle is $$0$$ deg. The shear plane angle is

In a typical metal cutting operation, using a cutting tool of positive rake $$\gamma = 10\deg ,$$ it was observed that the shear angle was $$20deg$$. The friction angle is