The paper attempts to study the machinability issues of aluminium-silicon carbide (Al-SiC) metal matrix composites (MMC) in turning using different grades of poly crystalline diamond (PCD) inserts. Al-SiC composite containing 15%wt of SiC was used as work material for turning and PCD inserts of three different grades were used as cutting tools. Experiments were conducted at various cutting speeds, feeds and depth of cuts and parameters, such as surface roughness, specific power consumed, and material removal rate were measured. The worn surface of the insert was examined by scanning electron microscope (SEM). The surface finish observed was found to be much lower than the theoretical surface roughness. The influence of cut was examined for the different grades of PCD inserts. It was observed that the 1600 grade PCD inserts performed well from the surface finish and specific power consumption points of view closely followed by the 1500 grade. © 2007 Springer-Verlag London Limited.