During orthogonal cutting of mild steel with a $$10$$ degrees rake angle tool the chip thickness ratio was obtained as $$0.4.$$ The shear angle (in degrees) evaluated from this data is

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