In forging operation the sticking friction condition occurs near the ...... (Center/ ends) while sliding friction condition occurs near the ...... (Center / ends)

For wire drawing operation, the work material should essentially be

A down sprue of $$180mm$$ length has diameter of $$20mm$$ at its top end. The liquid metal in the pouring cup is main-tained upto $$60$$ $$mm$$ height. What should be the theoretical diameter of down sprue at its lowest end to ensure that there is no aspiration effects.

Riser is designed so as to