The objective of the present work was to study the effect of the application of minimum quantity lubrication (MQL) in high-speed helical milling of Ti-6Al-4V compared with dry and flood coolant (wet) condition. The single factor experiment to study the relationship between cutting force, hole surface roughness and cutting parameters under various coolant-lubricant conditions were implemented. Tool life under various cooling conditions and fixed moderate cutting parameters have also been studied. Uniform flank wear, micro-chipping, thermal cracking and flaking were the dominant tool failure modes under all coolant-lubricant conditions. It was found that dry condition produced the poorest result in terms of cutting force, tool life and hole surface roughness as general expected. MQL presented comparable performance with flood condition in terms of cutting force and hole surface roughness, and even a better tool life performance than flood condition. This testified the flood condition can be replaced by the MQL condition, thus alleviating pollution and saving cost during helical milling of Ti-6Al-4V process.
