Electrical Discharge Truing for Sintered Polycrystalline Diamond Tools

Sintered polycrystalline diamond (PCD) is widely employed for cutting tools because of its great hardness and high wear resistance. However, it is extremely difficult to shape PCD micro tools by conventional machining methods. We describe the truing of a PCD micro tool by electrical discharge machining (EDM). The EDM mechanism and the EDM machinability for PCD are discussed. It is confirmed that insulated diamond grains in the PCD can be directly processed by EDM, because they are covered with an electrically conductive layer generated by applying discharge to the binder metal around them. Moreover, a short discharge duration of EDM is effective for improving the material removal rate and the surface roughness of PCD.