**1. Introduction**

Aluminum alloys (particularly 6000 and 7000 grades) are desirable in various industrial applications due to their high strength to weight ratio and good corrosion resistance. Aluminum has a low density of 2.7 g/cm3 compared to 7.87 g/cm3 for steels. It is generally lighter (about one to three times) than steel; however, its properties (i.e., Al 7075) in terms of specific strength and toughness are almost similar to some steel. In addition, aluminum alloys are relatively cost-effective and have good economic value [1]. Some industries that highly rely on aluminum alloys are aerospace, automotive, shipbuilding and rail companies. In the industries, machining operations, particularly drilling, are widely conducted to manufacture the components. Drilling of the components is usually performed at the end of manufacturing processes to produce holes for assembly of a final product using suitable fasteners. Some defects such as cracks, burr and surface deformation may be introduced during drilling operations which could lead to poor product performance and product failure. It is important for the dimension of the drilled holes to be within the tolerance and has minimum or no defect, so that the components can be assembled securely as a functional product.

Drilling efficiency is strongly dependent on the materials, tool geometry, cutting parameters and process conditions. Drilling aluminum alloy in a dry condition is challenging as it often results in poor drilled hole quality, which includes the formation of burr, high surface roughness and adhesion on the work material. After the drilling operation, the product will need additional finishing processes, such as reaming and deburring to achieve the required hole quality. To overcome such issues, drilling can be done with the presence of cutting fluid to reduce heat generation and hence reduce thermal softening and material adhesion. Nevertheless, it is important to note that the use of cutting fluid or lubricant during drilling is costly, could have a high environmental impact and requires high maintenance for disposal. Therefore, dry drilling is usually preferable, however, choosing appropriate cutting parameters is crucial to produce drilled holes with good quality for the product assembly.
