Comparative drilling studies have been carried out for a 20% Al2O3 microsphere reinforced Al metal matrix composite (MMC) using a (a) high speed steel (HSS) drill, (b) tungsten carbide (WC) drill and (c) polycrystalline diamond (PCD) drill. In this part of the paper, the flank wear characteristics of the drills have been presented. It is found that for the HSS drill a flank wear of 1.00 mm is reached in drilling for as little as 12 s. In contrast, under similar conditions for the WC drill, a flank wear of 0.16 mm was observed after drilling for a period of 600 s and in the case of the PCD drill, after 2210 s of drilling a flank wear of only 0.12 mm was observed. The PCD drill, however, showed some signs of chipping in the early stage, but this seemed to stabilize later on. Scanning electron microscopic (SEM) observations of the worn drill tips revealed that in addition to flank wear the HSS exhibited margin wear, the WC drill exhibited both margin wear and chisel edge wear and the PCD drill displayed crater wear.