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The main difficulties in machining composites and titanium are the excessive abrasive nature of the composite material and the poor thermal conductivity of titanium. When composites are combined with titanium in stacks, drilling them becomes even more difficult. Burrs and chips, which are produced when drilling the titanium, damage the composite layers and produce holes outside the required hole size accuracy. Although material stack-ups such as Carbon Fibre Reinforced Plastic/Titanium (CFRP/Ti) or CFRP/Al have been in industry for at least 20 years, more research is required regarding the influence of different drill geometry features on tool performance and hole quality while drilling these materials. The experiments reported in the literature have shown that drilling in CFRP/Ti stacks is a difficult task, as each of the materials requires a different approach, requiring extremely different types of drill geometry and cutting conditions.