If the Taylor's tool life exponent $$n$$ is $$0.2,$$ and the tool changing time is $$1.5$$ $$min,$$ then the tool life (in min) for maximum production rate is ____________

The main cutting force acting on a tool during the turning (orthogonal cutting) operation of a metal is $$400N.$$ The turning was performed using $$2mm$$ depth of cut and $$0.1mm/rev$$ feed rate. The specific cutting pressure (in $$N/m{m^2}$$ is

During pure orthogonal turning operation of a hollow cylindrical pipe, it is found that the thickness of the chip produced is $$0.5mm.$$ The feed given to the zero degree rake angle tool is $$0.2mm/rev.$$ The shear strain produced during the operation is ___________

Which one of the following instruments is widely used to check and calibrate geometric features of machine tools during their assembly?