The cutting of austempered ductile iron (ADI) was investigated in this study. Electro-discharge sinker machining (EDM) was employed to machine ADI materials by using a copper electrode, which was shaped into a different geometrical form. Machinability was evaluated in terms of the metal removal rate, electrode wear rate and surface finish within the machining conditions explored. A suitable pitch electrode was developed to machine ADI materials with higher removal rate and lower surface finish than those without a pitch electrode. The predictions were verified using an EDM process with appropriate reciprocation of the movement in the machining process. (C) 1999 Elsevier Science S.A. All rights reserved.