$6.$Which tool material offers the best combination of hardness and toughness for general machining applications?a$)$ High$-$speed steelb$)$ Carbidec$)$ Ceramicsd$)$ Cubic boron nitrideHow does the relief angle influence the cutting process?a$)$ It controls the width of the cutb$)$ It reduces friction between the tool and workpiecec$)$ It provides clearance between the tool and the workpieced$)$ It determines the depth of cutWhich tool angle is primarily responsible for controlling the chip flow direction?a$)$ Rake angleb$)$ Relief anglec$)$ Clearance angled$)$ Side cutting edge angle