In a rolling operation using rolls of diameter $$500mm,$$ if a thick plate cannot be reduced to less than $$20mm$$ in one pass, the coefficient of friction between the roll and the plate is ____________.

Which two of the following joining processes are autogeneous?
$$(i)$$ Diffusion welding
$$(ii)$$ Electro slag welding
$$(iii)$$ Tungsten inert gas welding
$$(iv)$$ Friction welding

Orthogonal turning of a mild steel tube with a tool of rake angle $${10^0}$$ is carried out at a feed of $$0.14$$ $$mm/rev.$$ If the thickness of the chip produced is $$0.28mm,$$ the values of shear angle and shear strain will be respectively.

A shaft of length $$90$$ $$mm$$ has a tapered portion of length $$55$$ $$mm.$$ The diameter of the taper is $$80$$ $$mm$$ at one end and $$65$$ $$mm$$ at the other. If the taper is made by tailstock set over method, the taper angle and the set over respectively are.