Comparison of between direct and peck drilling for large aspect ratio in Ti-6Al-4V alloy

Drilling is a crucial cutting operation as it represents 40 to 60% of the total material removed in the aircraft frame industry. Drilling difficult-to-cut materials, such as Ti-6Al-4V, is still a challenge due to their high chemical reactivity with different tool materials and low thermal conductivity. The application of cooling approach is needed to reduce the generated cutting temperature at the machining area. However, in drilling, the coolant does not sufficiently reach to the drill tip at the cutting zone because of the counter flow of the chips limits further penetration, especially in deep-hole drilling. To overcome such problems during direct drilling, different drilling techniques are followed. Peck drilling is among these methods in which the drilling process is conducted in a number of steps to achieve holes with large aspect ratio. The current study presents a detailed comparison between direct drilling and peck drilling of Ti-6Al-4V in terms of tool life, surface roughness, thrust force, torque, and burr formation. In terms of flank wear, thrust force, and burr formation, peck drilling showed better results when compared to direct drilling; however, direct drilling offers slightly better results in terms of surface quality.