Consider the following statements with respect to the relief angle of cutting tool:

$$1.$$ This affects the direction of chip flow.
$$2.$$ This reduces excessive friction between the tool and work piece
$$3.$$ This affects tool life
$$4.$$ This allows better access of coolant to the tool-work piece interface

Which of the statements given above are correct?

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

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

A non standard thread of pitch $$3.175$$ $$mm$$ is to be cut on a lathe having lead screw of pitch $$6$$ $$mm.$$ A change gear set provided with the lathe has one gear each with the following number of teeth: $$20, 30, 40, 50, 60, 70, 80,$$ $$90, 100, 110, 120, 127.$$ The correct pairs of change gears $$\left( {a/b\,\,x\,\,c/d} \right)$$ for machining the given thread are (assuming that the transmission ratio of the rest of the kinematic train between the lathe spindle and lead screw is equal to