Electric discharge machining tool electrode used

Electrodes for electric discharge machining are partially coated with pyrolytic boron nitride in order to prevent undesirable electric discharge between the electrode and a workpiece [330]. A boron nitride layer is used to prevent bonding of a conductive material, applied for indicating wear, to hard tool ceramics [331]. Equipment for applying pyrolytic boron nitride layers has been described [332], and also for applying boron nitride as protective sheets for immersion pyrometers for molten metals [333]. 

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