A rod of length $$20$$ $$mm$$ is stretched to make a rod of length $$40$$ $$mm.$$ Subsequently, it is compressed to make a rod of final length $$10$$ $$mm.$$ Consider the longitudinal tensile strain as positive and compressive strain as negative. The total true longitudinal strain in the rod is

In an orthogonal machining with a tool of $${9^ \circ }$$ orthogonal rake angle, the uncut chip thickness is $$0.2$$ $$mm.$$ The chip thickness fluctuates between $$0.25$$ $$mm$$ and $$0.4$$ $$mm.$$ The ratio of the maximum shear angle to the minimum shear angle during machining is ______________

During the turning of a $$20$$ $$mm-$$diameter steel bar at a spindle speed of $$400$$ $$rpm,$$ a tool life of $$20$$ minute is obtained. When the same bar is turned at $$200$$ $$rpm,$$ the tool life becomes $$60$$ $$minute.$$ Assume that Taylor's tool life equation is valid. When the bar is turned at $$300$$ $$rpm,$$ the tool life (in minute) is approximately

A cylindrical pin $$25_{ + 0.010}^{ + 0.020}\,\,mm$$ diameter is electroplated. Plating thickness is
$${2.0^{ \pm 0.005}}\,\,mm$$. Neglecting the gauge tolerance, the diameter (in $$mm,$$ up to $$3$$ decimal points accuracy) of the $$GO$$ ring gauge to inspect the plated pin is ___________