We describe the limit of miniaturization in micro-electrical discharge machining (EDM) using self-drilled holes. By this method, a microrod is machined using the edge of a hole drilled beforehand by the rod itself in the same setup. Hence, microrods can be machined very precisely without special equipment. To further decrease the minimum machinable diameter of microrods, the single-step forming method, double forming method, spark-out forming method, and step forming method were proposed. The minimum diameter was obtained by the single-step forming method. The straightest microrods were formed by the spark-out forming method.
