Patent ID: 6946615

Claim:
In an electric discharge machining method for machining a workpiece when machining electric power is supplied between said workpiece, which is made of insulating material or high resistance material coated with a conductive film, and an electrode, or machining electric power is supplied between said workpiece, which is made of insulating material or high resistance material coming into contact with conductive material, and an electrode so that pulse-like electric discharge is generated between said electrodes in a working solution containing carbon, said electric discharge machining method comprising the steps of: a voltage between said electrodes at a point of time when a predetermined period of time has passed from the start of electric discharge is measured; and a relatively short electric discharge pulse width suitable for machining said workpiece according to the measured value is set and a relatively long electric discharge pulse width suitable for forming a conductive film on a surface of said workpiece to be machined is set.