Verifying and finding the center of an EDM drilling electrode can be a delicate and troublesome task, especially as the electrode diameters become smaller (0.5mm / 0.020” Ø or smaller). To find the center of a tube electrode, utilize a table ball within the machine’s work zone. Pick-up accuracy diminishes as the electrode is extended from the supporting Die Guide because the electrode begins to flex and bend the further it is extended.

To improve probing pick-up accuracy, use a ½ sphere table ball, as this minimizes the length that the electrode is extended away from the die guide. The image below shows the electrode extension length differences between a standard 10mm (0.400”) Ø table ball and a 10mm ½ ball sphere with a 0.5mm (0.020”) Ø electrode. In this example, using a ½ sphere ball, the electrode extension distance from the die guide is reduced by 60% and will improve the probing accuracy. As an added benefit, the flat-top surface of the ½ sphere ball will also provide a more accurate and better-qualified surface to establish Z-depth pick-ups.