For cemented carbide tools, used for machining metals, there are three important properties of toughness, hardness and wear resistance to be optimized to achieve better performance. These properties are controlled by the volume fraction of the hard phase, e.g. tungsten carbide (WC), and the softer binder phase, e.g. Co (Cobalt), in case of WC-Co cutting inserts. Three carbide inserts (WC-Co) were examined by optical and electron microscopy to confirm that the ratios of the binder layer (Co) thickness (t) to the WC size (r) are 0.069, 0.12 and 0.035 respectively. By calculating the volume fraction of the two phases of WC and Co, discuss the properties of these three carbide inserts as; a) Which one has the highest hardness and why? b) Which one has the highest toughness and why? c) Which one has the highest resistance to wear and why?