cutting velocity

A low carbon steel bar of $$147$$ $$mm$$ diameter with length of $$630$$ $$mm$$ is being turned with uncoated carbide insert. The observed tool lives are $$24$$ and $$12$$ for cutt...

Tool life of a $$10$$ hours is obtained when cutting with a single point tool at $$63m/min.$$ If Taylor's constant $$C=257.35,$$ tool life on doubling the velocity will be

If under a condition of plain turning the life of the cutting tool decreases by $$50\% $$ due to increase in the cutting velocity by $$20\% $$, then what is the $$\% $$ increase in...