A $$\phi $$ $$20$$ $$mm$$ through hole is to be drilled in a $$30$$ $$mm$$ thick plate using a double fluted, $${120^ \circ }$$ lip angle drill. The drill tip is at a distance of $$3$$ $$mm$$ from the plate surface when cutting is started and an over travel of $$2$$ $$mm$$ is recommended as a margin to ensure drilling through the full thickness of the plate. If the drill rotates at $$500$$ $$rev/min$$ and the feed per tooth is $$0.01$$ $$mm,$$ the machining time of the operation (in sec) will be

A job of the shape shown in the figure below is to be machined on a lathe. The tool best suited for machining of this job must have

The cutting portion of a drill is to be welded to its shank. The process best suited for this is

Two identical cylindrical jobs are turned using (a) a round nosed tool of nose radius $$2$$ $$mm$$ and (b) a sharp corner tool having principal cutting edge angle $$ = {45^ \circ }$$ and auxiliary cutting edge angle $$ = {10^ \circ }$$. If the operation is carried out at a feed of $$0.08$$ $$mm/rev,$$ the heights of micro irregularities on the machined surfaces (in $$mm$$) in the two cases will be