The conventional CuW electrode used widely for high precision electrical discharge machining (EDM) is generally made by the melting method. However, its mixture ratio of copper to tungsten is structurally limited within a narrow range. On the other hand, the mixture ratio can readily be changed in the case of CuW made by the newly developed powder sintering method. In this study, in order to obtain a higher metal removal rate with a lower electrode wear rate, EDM characteristics for metal mold steel with the CuW electrode made by the new method were investigated with various mixture ratios. Experimental results clarified that the EDM characteristics are greatly changed by the Cu mixture ratio, and the electrode wear rate can be greatly decreased at the Cu mixture ratios of 10 - 20% under rough EDM conditions. It was also confirmed that much workpiece material and heat-resolved carbon adhere to the electrode surface at Cu mixture ratios of 10 - 20%, which plays an important role in reducing electrode wear.
