Most commonly copper electrodes are used for hole drilling in EDM machines. Much less common is use of graphite, tungsten carbide or copper tungster electrodes. Most commonly used electrode tube diameters are ranging from 0,1 mm to 14 mm, and their lengts vary from 150 mm to 400mm. Depends on needs of the job the nubber of channels inside the electrode can vary from standard 1 to 4 or more. The channels form different webs inside the tube, shapes of which are dependant on shape and quantity of channels.