Two aluminium alloy plates each $$10$$ $$mm$$ thick and $$1$$ $$m$$ long are welded without crowning by multipass tungsten inert gas butt welding. The joint configuration is $$V$$-type with $${60^ \circ }$$ angle and root gap is maintained at $$5$$ $$mm.$$ If electrode of $$5$$ $$mm$$ diameter with $$500$$ $$mm$$ length is used for welding, then the number of electrodes required is

In drilling operation, a twist-drill of $$30$$ $$mm$$ diameter with point angle of $$118$$ degrees is used. If the $$CNC$$ command issued to execute the drilling operation is $$G90$$ $$G01$$ $$Z??$$ $$F20.$$ The datum is defined on the top surface of the work material and the approach distance is $$3$$ $$mm.$$ Then, to achieve a cylindrical hole depth of $$40$$ $$mm,$$ the $$Z$$ coordinate to be provided in the $$CNC$$ command, in $$mm,$$ is ______________.

The angle of a twist drill that determines its rake angle is

During turning of mild steel work material, the maximum temperature is observed at