In which of the choices given below, the cutting tool materials are placed in the ascending order of permissible cutting speed for machining of steel?

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

A single point cutting tool with a nose radius of $$0.4$$ $$mm$$ was used to turn a component in a lathe employing a feed rate of $$0.3$$ $$mm/rev.$$ If the feed-rate is doubled, the ideal surface roughness (peak-to-valley height) produced on the component will increase by a factor of

Tool life equation for two tools under consideration are as follows

$$\eqalign{ & HSS:\,\,\,\,\,\,\,\,\,\,\,\,\,V{T^{0.2}} = 150 \cr & Carbide:\,\,\,\,\,\,V{T^{0.3}} = 250 \cr} $$
Where $$V$$ is the cutting speed in $$m/min$$ and $$T$$ is the tool life in $$min.$$ The breakdown cutting speed above which the carbide tool will be beneficial is