• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.38-44
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• 2017

The technology of electrical discharge tap machining may be appropriate for making thread out of highly brittle material. Especially, it is very difficult to machine tap with the traditional method if the brittle material has been hardened by quenching. In this study, the shape of electrical discharge blind hole tap machining was analyzed by discharge time, discharge current, and the flushing hole condition after quenched the tool steel of STD11 has discharged the tap shape with a screw-shaped copper(Cu) electrode. An experimental design was planned and analyzed by Taguchi robust experimental design. The result showed that the shape of the blind hole discharge tap was influenced by the flushing hole, discharge time, and discharge current. The most important factor of the processing conditions was found to be the discharge current. When blind hole EDM with a copper electrode with a flushing hole was conducted, the discharged shape was found to be smooth and the angle of the discharged tapped thread was also found to be close to the thread angle of $60^{\circ}$. As the values of discharge time and discharge current increased, the EDMed surface coarsened due to the increase of the single discharge energy and the shape of the thread collapsing.