In this study, we conducted a series of machining tests on an ultra-high precision machining centre to investigate the wear mechanism of diamond inserts when rough turning a rapidly solidified aluminium grade, having increased contents of hard elements such as iron, nickel and molybdenum particles. This aluminium grade (RSA 905) produced by melt-spinning process could be used for making optical moulds for plastic lens injection as a re-placement of other traditionally used aluminium grades. The study yields some recommendations on the best combination of machining parameters that will result in maximum material removal rates with smallest possible damage to the tool edge. In this work, standard non-controlled waviness mono-crystalline diamond inserts are used to cut the aluminium alloy. The initial results of tool wear measurements indicate that diamond machining of this particular aluminium grades results in relatively intensive tool wear compared to other optical material. The study concludes that the tool wear is very noticeable on the diamond inserts operated at high feed rates.