Effect of Graphite Electrode to Surface’s Characteristic of EDM Apiwat Muttamara, Warunee Borwornkiatkaew, Anuprong Pronpijit and Songkran Nuanchom MATEC Web Conf., 70 (2016) 01002 Published online: 11 August 2016 DOI: 10.1051/matecconf/20167001002