$13.$ Tool Failure Analysis: $-$ Outline the common modes of tool failure in machining. $-$ How does understanding tool failure contribute to process improvement? $-$ Discuss the role of preventive maintenance in minimizing tool failures$\mathrm{.}14.$ Tool Material Selection Criteria: $-$ What factors should be considered when selecting tool materials for a specific application? $-$ Discuss the trade$-$offs between hardness and toughness in tool material selection. $-$ How does the workpiece material influence the choice of cutting tool materials?$15.$ Non$-$traditional Machining Processes: $-$ Compare traditional and non$-$traditional machining processes.